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  • Wiley  (56,324)
  • Blackwell Publishing Ltd  (20,612)
  • American Geophysical Union  (12,784)
  • American Meteorological Society  (8,233)
  • Seismological Society of America (SSA)
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  • 1
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    Wiley
    In:  EPIC3The Ocean Floor : Bruce Heezen commemorative volume, (A Wiley-Interscience publication), Chichester, Wiley, pp. 147-163, ISBN: 0-471-10091-9
    Publication Date: 2014-05-12
    Description: The sedimentation regime off Northwest Africa is shaped by: (1) structur~al factors. which result in generallv low relief on land. shelf widths between 40 and more than 120 km. and av-erage sfope inclinations between 10 30' and 30; (2) land climates. which contral the delivery of terrigenous particles to the margin: (3) water movements including boundary currents and upwelling; and (4) the post- Pleistocene sea level rise. This chapter combines published and new results arising from research into the sedimentation processes off Northwest Africa. and emphasizes particularly the activities of the Kiel marine geological group during the past few years. Reviews of cruise activities and results were given in Closs et al. (1969) (Meteor cruise 8. 1967. off Morocco) . Seibold (1972) (Meteor cmise 25 . 1971. off Sahara to Central Senegal). Seibold and Hinz (1976) (Meteor cmise 39,1975 . and Valdivia cruise 10. 1975, from Morocco to South Senegal), and Waiden et al. (1974) (Meteor cmise 30, 1973, off Sierra Leone). Some of these cmises were used for pre- or post-site surveys for the Deep-Sea Drilling Project, or to add undisturbed Quaternary cores to the Glomar Challenger cores (leg 41, ] 975; Lancelot, et al .• 1978); leg 47 A, Arthur er al .• 1979; Lutze et al., 1979). We have concentrated our geological investigations on a number of standard profiles from the shelf to the upper continental rise as given in Figure 1. The manuscript was finished May 1979.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Inbook , peerRev
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  • 2
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    Wiley
    In:  EPIC3The Ocean Floor, The Ocean Floor, Wiley, pp. 147-163
    Publication Date: 2016-03-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Inbook , peerRev
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  • 3
    Publication Date: 2022-04-01
    Description: We present a workflow to estimate geostatistical aquifer parameters from pumping test data using the Python package welltestpy. The procedure of pumping test analysis is exemplified for two data sets from the Horkheimer Insel site and from the Lauswiesen site, Germany. The analysis is based on a semi‐analytical drawdown solution from the upscaling approach Radial Coarse Graining, which enables to infer log‐transmissivity variance and horizontal correlation length, beside mean transmissivity, and storativity, from pumping test data. We estimate these parameters of aquifer heterogeneity from type‐curve analysis and determine their sensitivity. This procedure, implemented in welltestpy, is a template for analyzing any pumping test. It goes beyond the possibilities of standard methods, for example, based on Theis' equation, which are limited to mean transmissivity and storativity. A sensitivity study showed the impact of observation well positions on the parameter estimation quality. The insights of this study help to optimize future test setups for geostatistical aquifer analysis and provides guidance for investigating pumping tests with regard to aquifer statistics using the open‐source software package welltestpy.
    Description: Article impact statement: We present a workflow to infer parameters of subsurface heterogeneity from pumping test data exemplified at two sites using welltestpy.
    Description: German Federal Environmental Foundation (DBU) http://dx.doi.org/10.13039/100007636
    Keywords: ddc:551.49
    Language: English
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  • 4
    Publication Date: 2022-04-01
    Description: In designed experiments, different sources of variability and an adequate scale of measurement need to be considered, but not all approaches in common usage are equally valid. In order to elucidate the importance of sources of variability and choice of scale, we conducted an experiment where the effects of biochar and slurry applications on soil properties related to soil fertility were studied for different designs: (a) for a field‐scale sampling design with either a model soil (without natural variability) as an internal control or with composited soils, (b) for a design with a focus on amendment variabilities, and (c) for three individual field‐scale designs with true field replication and a combined analysis representative of the population of loess‐derived soils. Three silty loam sites in Germany were sampled and the soil macroaggregates were crushed. For each design, six treatments (0, 0.15 and 0.30 g slurry‐N kg−1 with and without 30 g biochar kg−1) were applied before incubating the units under constant soil moisture conditions for 78 days. CO2 fluxes were monitored and soils were analysed for macroaggregate yields and associated organic carbon (C). Mixed‐effects models were used to describe the effects. For all soil properties, results for the loess sites differed with respect to significant contributions of fixed effects for at least one site, suggesting the need for a general inclusion of different sites. Analysis using a multilevel model allowed generalizations for loess soils to be made and showed that site:slurry:biochar and site:slurry interactions were not negligible for macroaggregate yields. The use of a model soil as an internal control enabled observation of variabilities other than those related to soils or amendments. Experiments incorporating natural variability in soils or amendments resulted in partially different outcomes, indicating the need to include all important sources of variability. Highlights Effects of biochar and slurry applications were studied for different designs and mixed‐effects models were used to describe the effects. Including an internal control allowed observation of, e.g., methodological and analytical variabilities. The results suggested the need for a general inclusion of different sites. Analysis using a multilevel model allowed generalizations for loess soils. The results indicated the need to include all important sources of variability.
    Keywords: ddc:631.4
    Language: English
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  • 5
    Publication Date: 2022-04-01
    Description: Temperate forest soils are often considered as an important sink for atmospheric carbon (C), thereby buffering anthropogenic CO2 emissions. However, the effect of tree species composition on the magnitude of this sink is unclear. We resampled a tree species common garden experiment (six sites) a decade after initial sampling to evaluate whether forest floor (FF) and topsoil organic carbon (Corg) and total nitrogen (Nt) stocks changed in dependence of tree species (Norway spruce—Picea abies L., European beech—Fagus sylvatica L., pedunculate oak—Quercus robur L., sycamore maple—Acer pseudoplatanus L., European ash—Fraxinus excelsior L. and small‐leaved lime—Tilia cordata L.). Two groups of species were identified in terms of Corg and Nt distribution: (1) Spruce with high Corg and Nt stocks in the FF developed as a mor humus layer which tended to have smaller Corg and Nt stocks and a wider Corg:Nt ratio in the mineral topsoil, and (2) the broadleaved species, of which ash and maple distinguished most clearly from spruce by very low Corg and Nt stocks in the FF developed as mull humus layer, had greater Corg and Nt stocks, and narrow Corg:Nt ratios in the mineral topsoil. Over 11 years, FF Corg and Nt stocks increased most under spruce, while small decreases in bulk mineral soil (esp. in 0–15 cm and 0–30 cm depth) Corg and Nt stocks dominated irrespective of species. Observed decadal changes were associated with site‐related and tree species‐mediated soil properties in a way that hinted towards short‐term accumulation and mineralisation dynamics of easily available organic substances. We found no indication for Corg stabilisation. However, results indicated increasing Nt stabilisation with increasing biomass of burrowing earthworms, which were highest under ash, lime and maple and lowest under spruce. Highlights We studied if tree species differences in topsoil Corg and Nt stocks substantiate after a decade. The study is unique in its repeated soil sampling in a multisite common garden experiment. Forest floors increased under spruce, but topsoil stocks decreased irrespective of species. Changes were of short‐term nature. Nitrogen was most stable under arbuscular mycorrhizal species.
    Description: Deutsche Forschungsgemeinschaff (DFG)
    Keywords: ddc:551.9 ; ddc:631.41
    Language: English
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  • 6
    Publication Date: 2022-03-11
    Description: As the Arctic coast erodes, it drains thermokarst lakes, transforming them into lagoons and, eventually, integrates them into subsea permafrost. Lagoons represent the first stage of a thermokarst lake transition to a marine setting and possibly more saline and colder upper boundary conditions. In this research, borehole data, electrical resistivity surveying, and modelling of heat and salt diffusion were carried out at Polar Fox Lagoon on the Bykovsky Peninsula, Siberia. Polar Fox Lagoon is a seasonally isolated water body connected to Tiksi Bay through a channel, leading to hypersaline waters under the ice cover. The boreholes in the centre of the lagoon revealed floating ice and a saline cryotic bed underlain by a saline cryotic talik, a thin ice‐bearing permafrost layer, and unfrozen ground. The bathymetry showed that most of the lagoon was ice‐grounded in spring. In bedfast ice areas, the electrical resistivity profiles suggest that an unfrozen saline layer was underlain by a thick layer of refrozen talik. The modelling suggests thermokarst lake taliks refreeze when submerged in saltwater with mean annual bottom water temperatures below or slightly above 0 °C. This occurs, because the top‐down chemical degradation of newly formed ice‐bearing permafrost is slower than the cooling of the talik. Hence, lagoons may pre‐condition taliks with a layer of ice‐bearing permafrost before encroachment by the sea and this frozen layer may act as a cap on gas migration out of the underlying talik.
    Repository Name: EPIC Alfred Wegener Institut
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  • 7
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    Wiley
    In:  EPIC3Journal of Geophysical Research-Atmospheres, Wiley, 127(3), pp. 1-18, ISSN: 0148-0227
    Publication Date: 2022-02-28
    Description: Fram Strait in the northern North Atlantic is a key region for marine cold air outbreaks (MCAOs), southward discharges of polar air under northerly air flow, which have a strong impact on air-sea heat fluxes, boundary layer processes and severe weather. This study investigates climatologies and decadal trends of Fram Strait MCAOs of different intensity classes based on the ERA5 reanalysis product for 1979–2020. Among striking interannual variability, it is shown that the main MCAO season is December through March, when MCAOs occur around 2/3 of the time. We report on significant decadal MCAO decreases in December and January, and a significant increase in March. While the mid-winter decrease is mainly related to the different paces of warming between the surface and the lower atmosphere, the increase in March can be related to changes in synoptic circulation patterns. As an explanation for the latter, a possible feedback between retreating Barents Sea sea ice, enhanced cyclonic activity and Fram Strait MCAOs is postulated. Exemplifying the trend toward stronger MCAOs during March, the study details the recordbreaking MCAO season in early 2020, and an observational case study of an extreme MCAO event in March 2020 is conducted. Thereby, radiosonde observations are combined with kinematic air back-trajectories to provide rare observational evidence for the diabatic cooling and drying during the MCAO preconditioning phase.
    Repository Name: EPIC Alfred Wegener Institut
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  • 8
    Publication Date: 2022-03-07
    Description: Fjords are recognized as hotspots of organic carbon (OC) burial in the coastal ocean. In fjords with glaciated catchments, glacier discharge carries large amounts of suspended matter. This sedimentary load includes OC from bedrock and terrigenous sources (modern vegetation, peat, soil deposits), which is either buried in the fjord or remineralized during export, acting as a potential source of CO2 to the atmosphere. In sub-Antarctic South Georgia, fjord-terminating glaciers have been retreating during the past decades, likely as a response to changing climate conditions. We determine sources of OC in surface sediments of Cumberland Bay, South Georgia, using lipid biomarkers and the bulk 14C isotopic composition, and quantify OC burial at present and for the time period of documented glacier retreat (between 1958 and 2017). Petrogenic OC is the dominant type of OC in proximity to the present-day calving fronts (60.4 ± 1.4% to 73.8 ± 2.6%) and decreases to 14.0 ± 2.7% outside the fjord, indicating that petrogenic OC is effectively buried in the fjord. Beside of marine OC, terrigenous OC comprises 2.7 ± 0.5% to 7.9 ± 5.9% and is mostly derived from modern plants and Holocene peat and soil deposits that are eroded along the flanks of the fjord, rather than released by the retreating fjord glaciers. We estimate that the retreat of tidewater glaciers between 1958 and 2017 led to an increase in petrogenic carbon accumulation of 22% in Cumberland West Bay and 6.5% in Cumberland East Bay, suggesting that successive glacier retreat does not only release petrogenic OC into the fjord, but also increases the capacity of OC burial.
    Repository Name: EPIC Alfred Wegener Institut
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  • 9
    Publication Date: 2022-04-24
    Description: Hillaire‐Marcelet al. bring forward several physical and geochemical arguments against our finding of an Arctic glaciolacustrine system in the past. In brief, we find that a physical approach to further test our hypothesis should additionally consider the actual bathymetry of the Greenland–Scotland Ridge (GSR), the density maximum of freshwater at 3–4°C, the sensible heat flux from rivers, and the actual volumes that are being mixed and advected. Their geochemical considerations acknowledge our original argument, but they also add a number of assumptions that are neither required to explain the observations, nor do they correspond to the lithology of the sediments. Rather than being additive in nature, their arguments of high particle flux, low particle flux, export of 230Th and accumulation of 230Th, are mutually exclusive. We first address the arguments above, before commenting on some misunderstandings of our original claim in their contribution, especially regarding our dating approach.
    Repository Name: EPIC Alfred Wegener Institut
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  • 10
    Publication Date: 2022-04-22
    Description: Integrated electron microprobe analyses (EMPAs) on glass and Sr–Nd isotope analyses have been performed on 17 tephras from the Middle Pleistocene Mercure lacustrine succession, southern Apennines. Two 40Ar/39Ar ages and the recognition of four relevant tephras from Colli Albani, Sabatini and possibly Roccamonfina volcanoes allowed us to ascribe the investigated succession to the late Marine Isotope Stage (MIS) 15–12 interval (560–440 ka). The Sr–Nd isotopes and major element glass compositions allowed us to attribute 10 out of the other 13 tephras to a poorly known activity of the Roccamofina volcano, whereas two layers were tentatively attributed to previously unknown Middle Pleistocene activity of Ponza Island or Campanian volcanoes, and one to Salina Island. The tephrostratigraphic correlation of the Mercure tephras with the Acerno lacustrine pollen record (Campania) also allowed us to evaluate the climatostratigraphic position of the tephras within the framework of the MIS 15–12 climatic variability. These results were obtained by combining the Sr–Nd isotope ratio with EMPA and 40Ar/39Ar geochronological data. This confirms the notable consistency of this approach for studying the Mediterranean Middle Pleistocene tephrostratigraphy, which, despite its great potential for both volcanology and Quaternary studies, has been hitherto barely explored.
    Description: Published
    Description: 232–248
    Description: 2V. Struttura e sistema di alimentazione dei vulcani
    Description: 3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici
    Description: 4V. Processi pre-eruttivi
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Description: JCR Journal
    Keywords: 40Ar/39Ar dating; EMPA glass compositions ; Middle Pleistocene; ; peri-Tyrrhenian explosive volcanisms ; Sr isotopes.
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 11
    Publication Date: 2022-05-03
    Description: Shallow seabed depressions attributed to focused fluid seepage, known as pock- marks, have been documented in all continental margins. In this study, we dem- onstrate how pockmark formation can be the result of a combination of multiple factors— fluid type, overpressures, seafloor sediment type, stratigraphy and bot- tom currents. We integrate multibeam echosounder and seismic reflection data, sediment cores and pore water samples, with numerical models of groundwa- ter and gas hydrates, from the Canterbury Margin (off New Zealand). More than 6800 surface pockmarks, reaching densities of 100 per km2, and an undefined number of buried pockmarks, are identified in the middle to outer shelf and lower continental slope. Fluid conduits across the shelf and slope include shal- low to deep chimneys/pipes. Methane with a biogenic and/or thermogenic origin is the main fluid forming flow and escape features, although saline and fresh- ened groundwaters may also be seeping across the slope. The main drivers of fluid flow and seepage are overpressure across the slope generated by sediment loading and thin sediment overburden above the overpressured interval in the outer shelf. Other processes (e.g. methane generation and flow, a reduction in hydrostatic pressure due to sea- level lowering) may also account for fluid flow and seepage features, particularly across the shelf. Pockmark occurrence coin- cides with muddy sediments at the seafloor, whereas their planform is elongated by bottom currents.
    Repository Name: EPIC Alfred Wegener Institut
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  • 12
    Publication Date: 2022-05-25
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Romagnoni, G., Kvile, K. o., Dagestad, K., Eikeset, A. M., Kristiansen, T., Stenseth, N. C., & Langangen, O. Influence of larval transport and temperature on recruitment dynamics of North Sea cod (Gadus morhua) across spatial scales of observation. Fisheries Oceanography, (2020): 1-16, doi:10.1111/fog.12474.
    Description: The survival of fish eggs and larvae, and therefore recruitment success, can be critically affected by transport in ocean currents. Combining a model of early‐life stage dispersal with statistical stock–recruitment models, we investigated the role of larval transport for recruitment variability across spatial scales for the population complex of North Sea cod (Gadus morhua ). By using a coupled physical–biological model, we estimated the egg and larval transport over a 44‐year period. The oceanographic component of the model, capable of capturing the interannual variability of temperature and ocean current patterns, was coupled to the biological component, an individual‐based model (IBM) that simulated the cod eggs and larvae development and mortality. This study proposes a novel method to account for larval transport and success in stock–recruitment models: weighting the spawning stock biomass by retention rate and, in the case of multiple populations, their connectivity. Our method provides an estimate of the stock biomass contributing to recruitment and the effect of larval transport on recruitment variability. Our results indicate an effect, albeit small, in some populations at the local level. Including transport anomaly as an environmental covariate in traditional stock–recruitment models in turn captures recruitment variability at larger scales. Our study aims to quantify the role of larval transport for recruitment across spatial scales, and disentangle the roles of temperature and larval transport on effective connectivity between populations, thus informing about the potential impacts of climate change on the cod population structure in the North Sea.
    Description: G.R. was supported by the Norden Top‐level Research Initiative sub‐programme “Effect Studies and Adaptation to Climate Change” through the Nordic Centre for Research on Marine Ecosystems and Resources under Climate Change (NorMER). K.Ø.K. was supported by the WHOI John H. Steele Post‐doctoral Scholar award and VISTA – a basic research program in collaboration between The Norwegian Academy of Science and Letters, and Equinor. We thank an anonymous referee for valuable comments that substantially improved the article.
    Keywords: Atlantic cod ; biophysical model ; larval transport ; North Sea ; populations ; stock–recruitment ; temperature
    Repository Name: Woods Hole Open Access Server
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  • 13
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 125(6), (2020): e2019JB019239, doi:10.1029/2019JB019239.
    Description: P‐to‐S‐converted waves observed in controlled‐source multicomponent ocean bottom seismometer (OBS) records were used to derive the Vp/Vs structure of Cascadia Basin sediments. We used P‐to‐S waves converted at the basement to derive an empirical function describing the average Vp/Vs of Cascadia sediments as a function of sediment thickness. We derived one‐dimensional interval Vp/Vs functions from semblance velocity analysis of S‐converted intrasediment and basement reflections, which we used to define an empirical Vp/Vs versus burial depth compaction trend. We find that seaward from the Cascadia deformation front, Vp/Vs structure offshore northern Oregon and Washington shows little variability along strike, while the structure of incoming sediments offshore central Oregon is more heterogeneous and includes intermediate‐to‐deep sediment layers of anomalously elevated Vp/Vs. These zones with elevated Vp/Vs are likely due to elevated pore fluid pressures, although layers of high sand content intercalated within a more clayey sedimentary sequence, and/or a higher content of coarser‐grained clay minerals relative to finer‐grained smectite could be contributing factors. We find that the proto‐décollement offshore central Oregon develops within the incoming sediments at a low‐permeability boundary that traps fluids in a stratigraphic level where fluid overpressure exceeds 50% of the differential pressure between the hydrostatic pressure and the lithostatic pressure. Incoming sediments with the highest estimated fluid overpressures occur offshore central Oregon where deformation of the accretionary prism is seaward vergent. Conversely, landward vergence offshore northern Oregon and Washington correlates with more moderate pore pressures and laterally homogeneous Vp/Vs functions of Cascadia Basin sediments.
    Description: This research was funded by National Science Foundation (NSF) Grant OCE‐1657237 to J. P. C, OCE‐1657839 to A. F. A. and S. H., and OCE‐1657737 to S. M. C. Data used in this study were acquired with funding from NSF Grants OCE‐1029305 and OCE‐1249353. Data used in this research were provided by instruments from the Ocean Bottom Seismic Instrument Center (http://obsic.whoi.edu, formerly OBSIP), which is funded by the NSF. OBSIC/OBSIP data are archived at the IRIS Data Management Center (http://www.iris.edu) under network code X6 (https://doi.org/10.7914/SN/X6_2012). Data processing was conducted with Emerson‐Paradigm Software package Echos licensed to Woods Hole Oceanographic Institution under Paradigm Academic Software Program and MATLAB package SeismicLab of the University of Alberta, Canada (http://seismic-lab.physics.ualberta.ca), under GNU General Public License (MATLAB® is a registered trademark of MathWorks).
    Description: 2020-11-28
    Keywords: Vp/Vs ; sediments ; ocean bottom seismometer ; Juan de Fuca plate ; Cascadia
    Repository Name: Woods Hole Open Access Server
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  • 14
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 125(8), (2020): e2020JC016068, doi:10.1029/2020JC016068.
    Description: Labrador Sea Water (LSW) is a major component of the deep limb of the Atlantic Meridional Overturning Circulation, yet LSW transport pathways and their variability lack a complete description. A portion of the LSW exported from the subpolar gyre is advected eastward along the North Atlantic Current and must contend with the Mid‐Atlantic Ridge before reaching the eastern basins of the North Atlantic. Here, we analyze observations from a mooring array and satellite altimetry, together with outputs from a hindcast ocean model simulation, to estimate the mean transport of LSW across the Charlie‐Gibbs Fracture Zone (CGFZ), a primary gateway for the eastward transport of the water mass. The LSW transport estimated from the 25‐year altimetry record is 5.3 ± 2.9 Sv, where the error represents the combination of observational variability and the uncertainty in the projection of the surface velocities to the LSW layer. Current velocities modulate the interannual to higher‐frequency variability of the LSW transport at the CGFZ, while the LSW thickness becomes important on longer time scales. The modeled mean LSW transport for 1993–2012 is higher than the estimate from altimetry, at 8.2 ± 4.1 Sv. The modeled LSW thickness decreases substantially at the CGFZ between 1996 and 2009, consistent with an observed decline in LSW volume in the Labrador Sea after 1994. We suggest that satellite altimetry and continuous hydrographic measurements in the central Labrador Sea, supplemented by profiles from Argo floats, could be sufficient to quantify the LSW transport at the CGFZ.
    Description: A. G. N. appreciates conversations with Kathy Donohue, Tom Rossby and Lisa Beal, which helped to interpret the results. J. B. P. acknowledges support from NSF through Grant OCE‐1947829. The authors thank all colleagues and ship crew involved in the R/V Meteor cruise M‐82/2 and Maria S. Merian cruise MSM‐21/2. The mooring data presented in this paper were funded by NSF through Grant OCE‐0926656.
    Description: 2021-01-03
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  • 15
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 47(3), (2020): e2019GL086703, doi:10.1029/2019GL086703.
    Description: Salt marsh assessments focus on vertical metrics such as accretion or lateral metrics such as open‐water conversion, without exploration of how the dimensions are related. We exploited a novel geospatial data set to explore how elevation is related to the unvegetated‐vegetated marsh ratio (UVVR), a lateral metric, across individual marsh “units” within four estuarine‐marsh systems. We find that elevation scales consistently with the UVVR across systems, with lower elevation units demonstrating more open‐water conversion and higher UVVRs. A normalized elevation‐UVVR relationship converges across systems near the system‐mean elevation and a UVVR of 0.1, a critical threshold identified by prior studies. This indicates that open‐water conversion becomes a dominant lateral instability process at a relatively conservative elevation threshold. We then integrate the UVVR and elevation to yield lifespan estimates, which demonstrate that higher elevation marshes are more resilient to internal deterioration, with an order‐of‐magnitude longer lifespan than predicted for lower elevation marshes.
    Description: This study was supported by the USGS through the Coastal Marine Hazards/Resources Program, the National Park Service through the Natural Resource Preservation Program, and the U.S. Fish and Wildlife Service through the Science Support Partnership. Erika Lentz, Elizabeth Pendleton, Meagan Gonneea, Joel Carr, and two anonymous reviewers provided constructive advice on the study. S.F. was partly supported by US National Science Foundation award 1637630 (PIE LTER), 1832221 (VCR LTER). The geospatial data used in this study are published in the Coastal Wetlands Synthesis Products catalog on ScienceBase (https://www.sciencebase.gov/catalog/item/5b73325ee4b0f5d5787c5ff3).
    Repository Name: Woods Hole Open Access Server
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  • 16
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research- Biogeosciences 125(4), (2020): e2019JG005158, doi:10.1029/2019JG005158.
    Description: Long‐term soil warming can decrease soil organic matter (SOM), resulting in self‐reinforcing feedback to the global climate system. We investigated additional consequences of SOM reduction for soil water holding capacity (WHC) and soil thermal and hydrological buffering. At a long‐term soil warming experiment in a temperate forest in the northeastern United States, we suspended the warming treatment for 104 days during the summer of 2017. The formerly heated plot remained warmer (+0.39 °C) and drier (−0.024 cm3 H2O cm−3 soil) than the control plot throughout the suspension. We measured decreased SOM content (−0.184 g SOM g−1 for O horizon soil, −0.010 g SOM g−1 for A horizon soil) and WHC (−0.82 g H2O g−1 for O horizon soil, −0.18 g H2O g−1 for A horizon soil) in the formerly heated plot relative to the control plot. Reduced SOM content accounted for 62% of the WHC reduction in the O horizon and 22% in the A horizon. We investigated differences in SOM composition as a possible explanation for the remaining reductions with Fourier transform infrared (FTIR) spectra. We found FTIR spectra that correlated more strongly with WHC than SOM, but those particular spectra did not differ between the heated and control plots, suggesting that SOM composition affects WHC but does not explain treatment differences in this study. We conclude that SOM reductions due to soil warming can reduce WHC and hydrological and thermal buffering, further warming soil and decreasing SOM. This feedback may operate in parallel, and perhaps synergistically, with carbon cycle feedbacks to climate change.
    Description: We would like to acknowledge Jeffery Blanchard, Priya Chowdhury, Kristen DeAngelis, Luiz Dominguez‐Horta, Kevin Geyer, Rachelle Lacroix, Xaiojun Liu, William Rodriguez, and Alexander Truchonand and for assistance with field sampling. We would like to acknowledge Michael Bernard for assistance with field sampling and lab work. We would like to acknowledge Aaron Ellison for statistical consultation. This research was financially supported by the U.S. National Science Foundation's Long Term Ecological Research Program (NSF‐DEB‐0620443 and NSF‐DEB‐1237491), the Long Term Research in Environmental Biology Program (NSF DEB‐1456528) , and the U.S. Department of Energy (DOE‐DE‐SC0005421 and DOE‐DE‐SC0010740). Data used in this study are available from the Harvard Forest Data Archive (Datasets HF018‐03, HF018‐04, and HF018‐13), accessible at https://harvardforest.fas.harvard.edu/harvard‐forest‐data‐archive.
    Description: 2020-10-04
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  • 17
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 33(9), (2020): 3845-3862, doi:10.1175/JCLI-D-19-0215.1.
    Description: The latitudinal structure of the Atlantic meridional overturning circulation (AMOC) variability in the North Atlantic is investigated using numerical results from three ocean circulation simulations over the past four to five decades. We show that AMOC variability south of the Labrador Sea (53°N) to 25°N can be decomposed into a latitudinally coherent component and a gyre-opposing component. The latitudinally coherent component contains both decadal and interannual variabilities. The coherent decadal AMOC variability originates in the subpolar region and is reflected by the zonal density gradient in that basin. It is further shown to be linked to persistent North Atlantic Oscillation (NAO) conditions in all three models. The interannual AMOC variability contained in the latitudinally coherent component is shown to be driven by westerlies in the transition region between the subpolar and the subtropical gyre (40°–50°N), through significant responses in Ekman transport. Finally, the gyre-opposing component principally varies on interannual time scales and responds to local wind variability related to the annual NAO. The contribution of these components to the total AMOC variability is latitude-dependent: 1) in the subpolar region, all models show that the latitudinally coherent component dominates AMOC variability on interannual to decadal time scales, with little contribution from the gyre-opposing component, and 2) in the subtropical region, the gyre-opposing component explains a majority of the interannual AMOC variability in two models, while in the other model, the contributions from the coherent and the gyre-opposing components are comparable. These results provide a quantitative decomposition of AMOC variability across latitudes and shed light on the linkage between different AMOC variability components and atmospheric forcing mechanisms.
    Description: The authors gratefully acknowledge support from the Physical Oceanography Program of the U.S. National Science Foundation (Awards OCE-1756143 and OCE-1537136) and the Climate Program Office of the National Oceanic and Atmospheric Administration (Award NA15OAR4310088). Gratitude is extended to Claus Böning and Arne Biastoch who shared ORCA025 output. S. Zou thanks F. Li, M. Buckley, and L. Li for helpful discussions. We also thank three anonymous reviewers for helpful suggestions.
    Keywords: Deep convection ; Ocean circulation ; Thermocline circulation
    Repository Name: Woods Hole Open Access Server
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  • 18
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 125(8), (2020): e2020JC016445, doi:10.1029/2020JC016445.
    Description: The Mid‐Atlantic Bight (MAB) Cold Pool is a bottom‐trapped, cold (temperature below 10°C) and fresh (practical salinity below 34) water mass that is isolated from the surface by the seasonal thermocline and is located over the midshelf and outer shelf of the MAB. The interannual variability of the Cold Pool with regard to its persistence time, volume, temperature, and seasonal along‐shelf propagation is investigated based on a long‐term (1958–2007) high‐resolution regional model of the northwest Atlantic Ocean. A Cold Pool Index is defined and computed in order to quantify the strength of the Cold Pool on the interannual timescale. Anomalous strong, weak, and normal years are categorized and compared based on the Cold Pool Index. A detailed quantitative study of the volume‐averaged heat budget of the Cold Pool region (CPR) has been examined on the interannual timescale. Results suggest that the initial temperature and abnormal warming/cooling due to advection are the primary drivers in the interannual variability of the near‐bottom CPR temperature anomaly during stratified seasons. The long persistence of temperature anomalies from winter to summer in the CPR also suggests a potential for seasonal predictability.
    Description: This work was funded by the National Oceanic and Atmospheric Administration through Awards NOAA‐NA‐15OAR4310133 and NOAA‐NA‐13OAR4830233 and the National Science Foundation Awards OCE‐1049088, OCE‐1419584, and OCE‐0961545.
    Description: 2021-02-03
    Keywords: Mid‐Atlantic Bight ; Cold Pool ; continental shelf ; temperature balance ; interannual variability ; near‐bottom temperature
    Repository Name: Woods Hole Open Access Server
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  • 19
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 125(8), (2020): e2020JC016197, doi:10.1029/2020JC016197.
    Description: Synoptic shipboard measurements, together with historical hydrographic data and satellite data, are used to elucidate the detailed structure of the Atlantic Water (AW) boundary current system in the southern Canada Basin and its connection to the upstream source of AW in the Chukchi Borderland. Nine high‐resolution occupations of a transect extending from the Beaufort shelf to the deep basin near 152°W, taken between 2003 and 2018, reveal that there are two branches of the AW boundary current that flow beneath and counter to the Beaufort Gyre. Each branch corresponds to a warm temperature core and transports comparable amounts of Fram Strait Branch Water between roughly 200–700 m depth, although they are characterized by a different temperature/salinity (T/S) structure. The mean volume flux of the combined branches is 0.87 ± 0.13 Sv. Using the historical hydrographic data, the two branches are tracked upstream by their temperature cores and T/S signatures. This sheds new light on how the AW negotiates the Chukchi Borderland and why two branches emerge from this region. Lastly, the propagation of warm temperature anomalies through the region is quantified and shown to be consistent with the deduced circulation scheme.
    Description: This work was funded by the following sources: National Science Foundation Grants PLR‐1504333, OPP‐1733564, and OPP‐1504394; National Oceanic and Atmospheric Administration Grant NA14OAR4320158; and National Aeronautics and Space Administration Grant NNX10AF42G.
    Description: 2021-01-27
    Repository Name: Woods Hole Open Access Server
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  • 20
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Hahn, L. C., Storelvmo, T., Hofer, S., Parfitt, R., & Ummenhofer, C. C. Importance of Orography for Greenland cloud and melt response to atmospheric blocking. Journal of Climate, 33(10), (2020): 4187-4206, doi:10.1175/JCLI-D-19-0527.1.
    Description: More frequent high pressure conditions associated with atmospheric blocking episodes over Greenland in recent decades have been suggested to enhance melt through large-scale subsidence and cloud dissipation, which allows more solar radiation to reach the ice sheet surface. Here we investigate mechanisms linking high pressure circulation anomalies to Greenland cloud changes and resulting cloud radiative effects, with a focus on the previously neglected role of topography. Using reanalysis and satellite data in addition to a regional climate model, we show that anticyclonic circulation anomalies over Greenland during recent extreme blocking summers produce cloud changes dependent on orographic lift and descent. The resulting increased cloud cover over northern Greenland promotes surface longwave warming, while reduced cloud cover in southern and marginal Greenland favors surface shortwave warming. Comparison with an idealized model simulation with flattened topography reveals that orographic effects were necessary to produce area-averaged decreasing cloud cover since the mid-1990s and the extreme melt observed in the summer of 2012. This demonstrates a key role for Greenland topography in mediating the cloud and melt response to large-scale circulation variability. These results suggest that future melt will depend on the pattern of circulation anomalies as well as the shape of the Greenland Ice Sheet.
    Description: This research was supported by the Woods Hole Oceanographic Institution Summer Student Fellow program, by the U.S. National Science Foundation under AGS-1355339 to C.C.U., and by the European Research Council through Grant 758005.
    Keywords: Ice sheets ; Blocking ; Cloud cover ; Topographic effects ; Climate change ; Climate variability
    Repository Name: Woods Hole Open Access Server
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  • 21
    Publication Date: 2022-03-16
    Description: Tectono-stratigraphic interpretation and sequential restoration modelling was performed over two high-resolution seismic profiles crossing the Western Ionian Basin of southern Italy. This analysis was undertaken in order to provide greater insights and a more reliable assessment of the deformation rate affecting the area. Offshore seismic profiling illuminates the sub-seafloor setting where a belt of active normal faults slice across the foot of the Malta Escarpment, a regional-scale structural boundary inherited from the Permo-Triassic palaeotectonic setting. A sequential restoration workflow was established to back-deform the entire investigated sector with the primary aim of analysing the deformation history of the three major normal faults affecting the area. Restoration of the tectono-stratigraphic model reveals how deformation rates evolved through time. In the early stage, the studied area experienced a significant deformation with the horizontal component prevailing over the vertical element. In this context, the three major faults contribute to only one third of the total deformation. The overall throw and extension then notably reduced through time towards the present day and, since the middle Pliocene, ongoing crustal deformation is accommodated almost entirely by the three major normal faults. Unloading and decompaction indicate that when compared to the unrestored seismic sections, a revision and a reduction of roughly one third of the vertical displacement of the faults offset is required. This analysis ultimately allows us to better understand the seismic potential of the region.
    Description: Published
    Description: 321-341
    Description: 2T. Deformazione crostale attiva
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 22
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    Wiley
    In:  EPIC3Limnology and Oceanography Letters, Wiley, 7(2), pp. 167-174, ISSN: 2378-2242
    Publication Date: 2022-03-25
    Description: The end of the polar night with the concurrent onset of photosynthetic biomass production ultimately leads to the spring bloom, which represents the most important event of primary production for the Arctic marine ecosystem. This dataset shows, for the first time, significant in situ biomass accumulation during the dark–light transition in the high Arctic, as well as the earliest recorded positive net primary production rates together with constant chlorophyll a-normalized potential for primary production through winter and spring. The results indicate a high physiological capacity to perform photosynthesis upon re-illumination, which is in the same range as that observed during the spring bloom. Put in context with other data, the results of this study indicate that also active cells originating from the low winter standing stock in the water column, rather than solely resting stages from the sediment, can seed early spring bloom assemblages.
    Repository Name: EPIC Alfred Wegener Institut
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  • 23
    Publication Date: 2022-03-01
    Description: To examine the atmospheric responses to Arctic sea ice variability in the Northern Hemisphere cold season (from October to the following March), this study uses a coordinated set of large-ensemble experiments of nine atmospheric general circulation models (AGCMs) forced with observed daily varying sea ice, sea surface temperature, and radiative forcings prescribed during the 1979–2014 period, together with a parallel set of experiments where Arctic sea ice is substituted by its climatology. The simulations of the former set reproduce the near-surface temperature trends in reanalysis data, with similar amplitude, and their multimodel ensemble mean (MMEM) shows decreasing sea level pressure over much of the polar cap and Eurasia in boreal autumn. The MMEM difference between the two experiments allows isolating the effects of Arctic sea ice loss, which explain a large portion of the Arctic warming trends in the lower troposphere and drive a small but statistically significant weakening of the wintertime Arctic Oscillation. The observed interannual covariability between sea ice extent in the Barents–Kara Seas and lagged atmospheric circulation is distinguished from the effects of confounding factors based on multiple regression, and quantitatively compared to the covariability in MMEMs. The interannual sea ice decline followed by a negative North Atlantic Oscillation–like anomaly found in observations is also seen in the MMEM differences, with consistent spatial structure but much smaller amplitude. This result suggests that the sea ice impacts on trends and interannual atmospheric variability simulated by AGCMs could be underestimated, but caution is needed because internal atmospheric variability may have affected the observed relationship.
    Description: Published
    Description: 8419–8443
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Keywords: Arctic ; Sea ice ; Atmospheric circulation ; Climate models ; 01.01. Atmosphere
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 24
    Publication Date: 2022-02-17
    Description: Free access at https://onlinelibrary.wiley.com/doi/10.1111/1755-6724.14824
    Description: Earthquake is a sudden release of energy due to fault motions. The severity of the damages can be minimized by development of a culture of prevention which includes the Seismic Hazard Assessment, microzonation studies and appropriate building codes. Earthquake risk assessment methods require seismo tectonic information usually organized in earthquake catalogues utilized in Probabilistic Seismic Hazard Assessment (PSHA) based on initial work by Cornell (1968), where probability distributions for magnitudes and source site distances reported in earthquake catalogues were utilized for the first time. In following years the method furtherly improved reporting an upper bound on the earthquake magnitude in each region avoiding the inclusion of unrealistically big earthquakes. A different approach has been followed in Countries characterized by significant incompletenesses in available earthquake catalogues. In these places the Deterministic Seismic Hazard Assessment (DSHA) methods have been often utilized. In particular the DSHA takes into account the maximum possible earthquake to evaluate the intensity of seismic ground motion distribution at a site by taking account the seismotectonic setup of the area. A deepening in the knowledge of seismotectonics and of morphostructural features of the studied area has been carried out in pattern recognition studies (Gelfand et al., 1976 and references therein). More updated applications named Neo-Deterministic Seismic Hazard Assessment (NDSHA) proposed by Wang et al. (2021) also consider morphostructural zoning which, in turn, considers nodes (fractured areas), lineaments and topographical features like the maximal elevation and the minimal elevation of the studied area. The steepness of topographic surfaces and sharp variations in morphostructural parameters indicate high tectonic activity. Some geological features are also presently utilized in PSHA methods in some Countries and considers basic parameters like the top and the bottom of seismogenic layers deduced by faults geometry within the frame of the Earthquake Rupture Forecasting (Bird and Liu, 2007).
    Description: Published
    Description: 31-33
    Description: 9T. Geochimica dei fluidi applicata allo studio e al monitoraggio di aree sismiche
    Description: JCR Journal
    Keywords: probabilistic seismic hazard assessment, deterministic seismic hazard assessment, helium isotopes, geochemical prospection, earthquake precursors ; seismic hazard estimation by geochemical methods
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  • 25
    Publication Date: 2022-02-21
    Description: Relative sea‐level (RSL) evolution during Marine Isotopic Stage (MIS) 5 in the Mediterranean basin is still not fully understood despite a plethora of morphological, stratigraphic and geochronological studies carried out on highstand deposits of this area. In this review we assembled a database of 323 U/Th‐dated samples (e.g. corals, molluscs, speleothems) which were used to chronologically constrain RSL evolution within MIS 5. The application of strict geochemical criteria to the U/Th samples indicates that only ~33% of data available for the Mediterranean Sea can be considered ‘reliable’. Most of these data (~65%) refer to the MIS 5e highstand, while only ~17% could be related to the MIS 5a. No attribution to MIS 5c can be unequivocally supported. Nevertheless, the resulting framework does not allow us to define a satisfactory RSL trend during the MIS 5e highstand and subsequent MIS 5 substages. Overall, the proposed selection of reliable/unreliable data would be useful for detecting areas where MIS 5 substage attributions are not supported by confident U/Th chronological data and thus the related reconstructions need to be revised. In this regard, the resulting framework calls for a reappraisal and re‐examination of the Mediterranean records with advanced geochronological methodologies.
    Description: Published
    Description: 1174-1189
    Description: 5A. Ricerche polari e paleoclima
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 26
    Publication Date: 2022-02-25
    Description: The Apennines are a retreating collisional belt where the foreland basin system, across large domains, is floored by a subaerial forebulge unconformity developed due to forebulge uplift and erosion. This unconformity is overlain by a diachronous sequence of three lithostratigraphic units made of (a) shallow-water carbonates, (b) hemipelagic marls and shales and (c) siliciclastic turbidites. Typically, the latter two have been interpreted regionally as the onset of syn-orogenic deposition in the foredeep depozone, whereas little attention has been given to the underlying unit. Accordingly, the rate of migration of the central-southern Apennine fold-thrust beltforeland basin system has been constrained, so far, exclusively considering the age of the hemipelagites and turbidites, which largely post-date the onset of foredeep depozone. In this work, we provide new high-resolution ages obtained by strontium isotope stratigraphy applied to calcitic bivalve shells sampled at the base of the first syn-orogenic deposits overlying the Eocene-Cretaceous pre-orogenic substratum. Integration of our results with published data indicates progressive rejuvenation of the strata sealing the forebulge unconformity towards the outer portions of the foldthrust belt. In particular, the age of the forebulge unconformity linearly scales with the pre-orogenic position of the analysed sites, pointing to an overall constant migration velocity of the forebulge wave in the last 25 Myr.
    Description: Published
    Description: 2817-2836
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Description: JCR Journal
    Keywords: central-southern Apennines (Italy) ; fold-thrust belt ; forebulge ; foredeep
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 27
    Publication Date: 2022-01-07
    Description: Vegetation biomass is a globally important climate-relevant terrestrial carbon pool. Landsat, Sentinel-2 and Sentinel-1 satellite missions provide a landscape-level opportunity to upscale tundra vegetation communities and biomass in high latitude terrestrial environments. We assessed the applicability of landscape-level remote sensing for the low Arctic Lena Delta region in Northern Yakutia, Siberia, Russia. The Lena Delta is the largest delta in the Arctic and is located North of the treeline and the 10 °C July isotherm at 72° Northern Latitude in the Laptev Sea region. During the LENA2018 expedition, we set up plots for plant projective cover and Above Ground Biomass (AGB) and sampled shrubs for shrub-ring analyses. AGB is providing the magnitude of the carbon flux, whereas stand age is irreplaceable to provide the cycle rate. AGB data and shrub age data clearly show a separation between i) low disturbance landscape types with dominant AGB moss contribution, but always low vascular plant AGB (〈0.5 kg m-2) characterised by old shrubs of several decades of stand age versus ii) a much higher vascular plant AGB contribution (〉 0.5 kg m-2) with only young shrubs in high disturbance regimes. The low disturbance regimes are represented on the Holocene and Pleistocene delta terraces in form of azonal polygonal tundra complexes and softly dissected valleys with zonal tussock tundra. In contrast, the high disturbance regimes are sites of thermo-erosion such as along thermo-erosional valleys and on floodplains. We upscaled AGB and above ground carbon pool ages using a Sentinel-2 satellite acquisition from early August 2018. We classified via classification training using Elementary Sampling Units that are the 30 m x 30 m vegetation field plots. We then used the land cover classes and grouped them according to their settings either in high disturbance or low disturbance regimes with each associated AGB value ranges and shrub age regimes. We also evaluated circum-Arctic harmonized ESA GlobPermafrost land cover and vegetation height remote sensing products covering subarctic to Arctic land cover types for the central Lena Delta. The products are freely available and published in the PANGAEA data repository under https://doi.org/10.1594/PANGAEA.897916 and https://doi.org/10.1594/PANGAEA.897045. ESA GlobPermafrost land cover and vegetation height remote sensing products and our Sentinel-2 derived AGB product for the central Lena Delta shows realistic spatial patterns of landcover classes and biomass distribution at landscape level. However, in all products, the high biomass patches of high shrubs in the tundra landscape could not spatially be resolved as they are confined to patchy and linear distribution, not representing large enough areas suitable for upscaling. We found that high disturbance regimes with linked high and rapid AGB fluxes are distributed mainly on the floodplains and as patches along thermoerosioal features, e.g. valleys. Whereas the low disturbance landscapes on Yedoma upland tundra and Holocene terraces occur with larger area coverage representing decades slower and in magnitude smaller AGB fluxes.
    Repository Name: EPIC Alfred Wegener Institut
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  • 28
    Publication Date: 2022-01-04
    Description: We present a novel method to estimate dynamic ice loss of Greenland's three largest outlet glaciers: Jakobshavn Isbræ, Kangerlussuaq Glacier, and Helheim Glacier. We use Global Navigation Satellite System (GNSS) stations attached to bedrock to measure elastic displacements of the solid Earth caused by dynamic thinning near the glacier terminus. When we compare our results with discharge, we find a time lag between glacier speedup/slowdown and onset of dynamic thinning/thickening. Our results show that dynamic thinning/thickening on Jakobshavn Isbræ occurs 0.87 ± 0.07 years before speedup/slowdown. This implies that using GNSS time series we are able to predict speedup/slowdown of Jakobshavn Isbræ by up to 10.4 months. For Kangerlussuaq Glacier the lag between thinning/thickening and speedup/slowdown is 0.37 ± 0.17 years (4.4 months). Our methodology and results could be important for studies that attempt to model and understand mechanisms controlling short-term dynamic fluctuations of outlet glaciers in Greenland.
    Repository Name: EPIC Alfred Wegener Institut
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  • 29
    Publication Date: 2021-11-29
    Description: This work presents a novel empirical Ground Motion prediction Model (GMM) for vertical-to-horizontal (VH) response spectral amplitudes up to 10 s, peak ground acceleration and velocity for shallow crustal earthquakes in Italy. Being calibrated on the most up-to-date strong motion dataset for Italian crustal earthquakes (ITA18), the model is consistent with the ITA18 GMM for the horizontal ground motion. This property makes the model useful in probabilistic seismic hazard assessment for Italy to derive compatible vertical and horizontal response spectra. To account for the increase of VH ratios in the proximity of the seismic source, an adjustment term is introduced to improve the prediction capability of the model in near-source conditions, relying on the worldwide NEar-Source Strong motion dataset (NESS). The proposed model uses a simple functional form restricted to a limited number of predictor variables, namely, magnitude, source-to-site distance, focal mechanism, and site effects, and the variability associated with both VH and V models is provided.
    Description: Published
    Description: 4121-4141
    Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 30
    Publication Date: 2021-12-16
    Description: Diffusive gradients in thin fi lms (DGT) have been tested in CO2-rich, metal-bearing fl uids from springs in the Campo de Calatrava region in Central Spain, to assess their applicability as a monitoring tool in onshore CO2 storage projects. These fi lms are capable of adsorbing metals and recording changes in their concentration in water, sediments, and soils. Considering that CO2 dissolution promotes metal solubilization and transport, the use of these fi lms could be valuable as a monitoring tool of early leakage. A number of DGT have been deployed in selected springs with constant metal concentration. The studied waters show high concentrations of Fe, as high as 1 × 104 μg·L–1, Ni, Co, Zn, Cu, and Mn. Comparing re-calculated metal concentration in DGT with metal water concentration, two different metal behaviors are observed: (i) metals with sorption consistent with the metal concentration (i.e. plotting close to the 1:1 line in a [Me]DGT: [Me]water plot), and (ii) metals with non–linear sorption, with some data showing metal enrichment in DGT compared with the concentration in water. Metals in the fi rst group include Fe, Mn, Co, Ni, and U, and metals in the second group are Zn, Pb, Cr, Cu, and Al. From this research, it is concluded that the metals in the fi rst group can be used to monitor potential leakage by using DGT, providing effective leakage detection even considering low variations of concentrations, episodic metal release, and reducing costs compared with conventional, periodic water sampling.
    Description: Published
    Description: 163-175
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Description: JCR Journal
    Keywords: Campo de Calatrava ; CO2 storage and leakage ; DGT ; metal leakage ; metal transport ; trace metals ; 03.04. Chemical and biological ; 05.04. Instrumentation and techniques of general interest
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  • 31
    Publication Date: 2021-12-22
    Description: We present a new geometrical method capable of quantifying and illustrating the outcomes of a three-component mixing dynamics. In a three-component mixing sce nario, classical algebraic equations and endmember mixing analysis (EMMA) can be used to quantify the contributions from each fraction. Three-component mixing of natural waters, either in an element–element plot or by using the EMMA mixing sub space is described by a triangular shaped distribution of sample points where each endmember is placed on an apex, while each side corresponds to the mixing function of the two endmembers placed at the apex, considering the third endmembers' con tribution equal to zero. Along each side, the theoretical mixing fractions can be com puted using mass balance equations. Samples with contributions from three endmembers will plot inside the triangle, while the homogeneous barycentric coordi nate projections can be projected onto the three sides. The geochemistry observed in the mineralized Ferrarelle aquifer system (southern Italy) results from three component mixing of groundwater, each with diagnostic geochemical compositions. The defined boundary conditions allow us to parameterize and validate the proce dures for modelling mixing, including selection of suitable geochemical tracer
    Description: Published
    Description: e14409
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Description: JCR Journal
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  • 32
    Publication Date: 2022-02-10
    Description: Muography represents a recent and innovative tool for investigating the interior of active volcanoes. However, when dealing with frequently erupting open-vent volcanoes such as Stromboli, any result should take into con- sideration the structural and morphology changes caused by the eruptive activity. This may cause either summit collapses by magma withdrawal, or morphology growth by the accumulations of a fallout from the explosive activity, or more often a combination of both. In this chapter, we present an integration of various techniques, comprising muography and digital elevation model reconstruction, together with GBInSAR ground deformation and volcano seismicity, to reconstruct the geometry of the shallow magma supply system of the volcano and its changes in time. We show how muography can display the interior of the volcano as well as its outer growth, being sensitive to all volume changes that occurred between the framed surface and the detector. This was discovered in Stromboli by comparing digital topography in the interval between 2010 and 2012, when the rapid growth of the volcano summit by the accumulation of ballistic products in the area between the crater zone and the muon detec- tor occurred. This deposit, together with the filling in of the graben-like depression, formed during the 2007 eruption, by fallout during the persistent explosive activity, contributed to generating a remarkable anomaly in the summit area of the volcano visualized by muography. In addition, the shallow feeding system of the volcano was surveyed by GBInSAR and seismicity, which allowed us to reconstruct its path up to a depth of a few hundred meters.
    Description: Published
    Description: 75-91
    Description: 2V. Struttura e sistema di alimentazione dei vulcani
    Keywords: Stromboli volcano ; Shallow supply system ; Muography of active volcanoes
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 33
    Publication Date: 2022-02-14
    Description: The influence of the Atlantic multidecadal variability (AMV) on the North Atlantic storm track and eddy-driven jet in the winter season is assessed via a coordinated analysis of idealized simulations with state-of-the-art coupled models. Data used are obtained from a multimodel ensemble of AMV± experiments conducted in the framework of the Decadal Climate Prediction Project component C. These experiments are performed by nudging the surface of the Atlantic Ocean to states defined by the superimposition of observed AMV± anomalies onto the model climatology. A robust extratropical response is found in the form of a wave train extending from the Pacific to the Nordic seas. In the warm phase of the AMV compared to the cold phase, the Atlantic storm track is typically contracted and less extended poleward and the low-level jet is shifted toward the equator in the eastern Atlantic. Despite some robust features, the picture of an uncertain and model-dependent response of the Atlantic jet emerges and we demonstrate a link between model bias and the character of the jet response.
    Description: Published
    Description: 347-360
    Description: 4A. Oceanografia e clima
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 34
    Publication Date: 2022-01-11
    Description: Mt Etna has made headlines over the last weeks and months with spectacular eruptions, some of them highly explosive. This type of paroxysmal eruptive behaviour is characteristic of Etna’s activity over the past few decades and so it is no surprise that Etna is among the most active volcanoes worldwide. Etna is well-known for its extraordinary geology and due to its repeated eruptive activity it provides a continuous supply of new scientific opportunities to understand the inner workings of large basaltic volcanic systems. In addition to its scientific value, Etna is also a world famous tourist attraction and has been listed as a UNESCO World Heritage site in 2013 for its geological and cultural value and not least for its fine agricultural products. Etna’s status as an iconic volcano is not a recent phenomenon; in fact, Etna has been a literary fixture for at least 3000 years, giving rise to many ancient myths and legends that mark it as a special place, deserving of human respect. From the ancient eruptions to the latest events in February–April 2021, people try to explain and understand the processes that occur within and beneath the volcano. In this article, we briefly summarize the recent eruptive activity of Etna as well as the ancient myths and legends that surround this volcano, from the underground forge of Hephaestus to the adventures of Odysseus, all the way to the benefits and dangers the volcano provides to those living on its flanks today.
    Description: Published
    Description: 141-149
    Description: 2TM. Divulgazione Scientifica
    Description: N/A or not JCR
    Keywords: Etna, mythology, 2021 paroxysms, economy ; 04.08. Volcanology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 35
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    American Geophysical Union
    In:  EPIC3Paleoceanography and Paleoclimatology, American Geophysical Union, 37(2), pp. e2020PA003953, ISSN: 2572-4517
    Publication Date: 2022-02-15
    Description: Cenozoic climate changes have been linked to tectonic activity and variations in atmospheric CO2 concentrations. Here we present Miocene and Pliocene sensitivity experiments performed with the climate model COSMOS. The experiments contain changes with respect to paleogeography, ocean gateway configuration, and atmospheric CO2 concentrations, as well as a range of vertical mixing coefficients in the ocean. For the Mid-Miocene, we show that the impact of ocean mixing on surface temperature is comparable to the effect of the possible range in reconstructed CO2 concentrations. In combination with stronger vertical mixing, relatively moderate CO2-concentrations of 450 ppmv enable global mean surface, deep-water and meridional temperature characteristics representative of Mid-Miocene Climatic Optimum (MMCO) reconstructions. The Miocene climate shows a reduced meridional temperature gradient and reduced seasonality. In the case of enhanced mixing, surface and deep ocean temperatures show significant warming of up to 5-10°C and an Arctic temperature anomaly of more than 12°C. In the Pliocene simulations, the impact of vertical mixing and CO2 is less important for the deep ocean, which we interpret as a different sensitivity dependence on the background state and mixed layer dynamics. We find a significant reduction in surface albedo and effective emissivity for either a high level of atmospheric CO2 or increased vertical mixing. Our mixing sensitivity experiments provide a warm deep ocean via ocean heat uptake. We propose that the mixing hypothesis can be tested by reconstructions of the thermocline and seasonal paleoclimate data indicating a lower seasonality relative to today.
    Repository Name: EPIC Alfred Wegener Institut
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  • 36
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    Unknown
    American Geophysical Union
    In:  EPIC3American Geophysical Union Conference 2021, Hybrid Online and in New Orleans, 2021-12-13-2021-12-17AGU 2021, American Geophysical Union
    Publication Date: 2022-02-15
    Description: As air temperatures rise and sea ice cover declines in the Arctic, permafrost coastal cliffs thaw more rapidly and wave energy rises. Thus, as the open water season continues to lengthen, climate change triggers a large part of the Arctic shoreline to become increasingly vulnerable to erosion. Arctic erosion supplies nutrient-laden and carbon-rich sediment into nearshore ecosystems. A retreating coastline also has consequences for residential, cultural, and industrial infrastructure. Despite its importance, erosion is currently neglected in global climate models, and existing physics-based numerical models of Arctic shoreline erosion are too complex and regionally-focused to be applied on a pan-Arctic scale. Here, we apply our simplified numerical erosion model, ArcticBeach v1.0, to the entire Arctic coastline. ArcticBeach v1.0 has previously been shown to simulate retreat rates at two sites that differ substantially in their main mechanisms of retreat (sub-aerial erosion/thaw slumping versus notch/block erosion). The model uses heat and sediment volume balances in order to predict horizontal cliff retreat and vertical erosion of a fronting beach. It contains an erosion module that uses empirical equations to estimate cross-shore sediment transport, coupled to a storm surge module forced by wind. We present Arctic maps of regional variation in trends in 2-meter air temperature, sea ice concentration, and wind speed.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 37
    Publication Date: 2022-07-04
    Description: Collapse of permafrost coasts delivers large quantities of particulate organic carbon (POC) to arctic coastal areas. With rapidly‐changing environmental conditions, sediment and organic carbon (OC) mobilization and transport pathways are also changing. Here, we assess the sources and sinks of POC in the highly‐dynamic nearshore zone of Herschel Island ‐ Qikiqtaruk (Yukon, Canada). Our results show that POC concentrations sharply decrease, from 15.9 to 0.3 mg L‐1, within the first 100 – 300 meters offshore. Simultaneously, radiocarbon ages of POC drop from 16,400 to 3,600 14C years, indicating rapid settling of old permafrost POC to underlying sediments. This suggests that permafrost OC is, apart from a very narrow resuspension zone (〈5 m water depth), predominantly deposited in nearshore sediments. While long‐term storage of permafrost OC in marine sediments potentially limits biodegradation and its subsequent release as greenhouse gas, resuspension of fine‐grained, OC‐rich sediments in the nearshore zone potentially enhances OC turnover.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed , info:eu-repo/semantics/article
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  • 38
    Publication Date: 2022-06-21
    Description: Author Posting. © American Meteorological Society, 2022. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 52(6),(2022): 1191-1204, https://doi.org/10.1175/jpo-d-21-0242.1.
    Description: A simplified quasigeostrophic (QG) analytical model together with an idealized numerical model are used to study the effect of uneven ice–ocean stress on the temporal evolution of the geostrophic current under sea ice. The tendency of the geostrophic velocity in the QG model is given as a function of the lateral gradient of vertical velocity and is further related to the ice–ocean stress with consideration of a surface boundary layer. Combining the analytical and numerical solutions, we demonstrate that the uneven stress between the ice and an initially surface-intensified, laterally sheared geostrophic current can drive an overturning circulation to trigger the displacement of isopycnals and modify the vertical structure of the geostrophic velocity. When the near-surface isopycnals become tilted in the opposite direction to the deeper ones, a subsurface velocity core is generated (via geostrophic setup). This mechanism should help understand the formation of subsurface currents in the edge of Chukchi and Beaufort Seas seen in observations. Furthermore, our solutions reveal a reversed flow extending from the bottom to the middepth, suggesting that the ice-induced overturning circulation potentially influences the currents in the deep layers of the Arctic Ocean, such as the Atlantic Water boundary current.
    Description: This work was funded by the National Key Research and Development Program of China (Grant 2017YFA0604600), the National Natural Science Foundation of China (Grant 41676019), the Fundamental Research Funds for the Central Universities (Grant 2019B81214), the Postgraduate Research and Practice Innovation Program of Jiangsu Province (Grant KYCX19_0384), and the National Science Foundation (MAS, Grants OPP-1822334, OCE-2122633).
    Keywords: Arctic ; Sea ice ; Channel flows ; Vertical motion ; Ekman pumping ; Idealized models ; Quasigeostrophic models
    Repository Name: Woods Hole Open Access Server
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  • 39
    Publication Date: 2022-06-27
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Suca, J., Ji, R., Baumann, H., Pham, K., Silva, T., Wiley, D., Feng, Z., & Llopiz, J. Larval transport pathways from three prominent sand lance habitats in the Gulf of Maine. Fisheries Oceanography, 31(3), (2022): 333– 352, https://doi.org/10.1111/fog.12580.
    Description: Northern sand lance (Ammodytes dubius) are among the most critically important forage fish throughout the Northeast US shelf. Despite their ecological importance, little is known about the larval transport of this species. Here, we use otolith microstructure analysis to estimate hatch and settlement dates of sand lance and then use these measurements to parametrize particle tracking experiments to assess the source–sink dynamics of three prominent sand lance habitats in the Gulf of Maine: Stellwagen Bank, the Great South Channel, and Georges Bank. Our results indicate the pelagic larval duration of northern sand lance lasts about 2 months (range: 50–84 days) and exhibit a broad range of hatch and settlement dates. Forward and backward particle tracking experiments show substantial interannual variability, yet suggest transport generally follows the north to south circulation in the Gulf of Maine region. We find that Stellwagen Bank is a major source of larvae for the Great South Channel, while the Great South Channel primarily serves as a sink for larvae from Stellwagen Bank and Georges Bank. Retention is likely the primary source of larvae on Georges Bank. Retention within both Georges Bank and Stellwagen Bank varies interannually in response to changes in local wind events, while the Great South Channel only exhibited notable retention in a single year. Collectively, these results provide a framework to assess population connectivity among these sand lance habitats, which informs the species' recruitment dynamics and impacts its vulnerability to exploitation.
    Description: Funding came from the National Oceanic and Atmospheric Administration Woods Hole Sea Grant Program (Woods Hole Sea Grant, Woods Hole Oceanographic Institution, NA18OAR4170104, Project No. R/O-57; RJ, HB, and JKL), the Bureau of Ocean Energy Management (IA agreement M17PG0019; DNW, HB, and JKL) including a subaward via the National Marine Sanctuary Foundation (18-11-B-203), and a National Science Foundation Long-term Ecological Research grant for the Northeast US Shelf Ecosystem (OCE 1655686; RJ and JKL). JJS was funded by the National Science Foundation Graduate Research Fellowship program.
    Keywords: Gulf of Maine ; larval retention ; otolith microstructure ; particle tracking ; population connectivity ; sand lance
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  • 40
    Publication Date: 2022-05-24
    Description: We have reinterpreted the causative fault parameters of the 2005 Zarand earthquake in the light of a new imagery study using Interferometric Synthetic Aperture Radar (InSAR). By conducting a joint inversion of two InSAR datasets, we can characterize the rupture as it relates to complex local structures. At first, the mainshock ruptured a nearly pure reverse fault, dipping ~65° NNW in the basement below the southeastern area of Zarand. Two more fault segments were subsequently activated: an oblique‐normal fault segment parallel to the first segment, dipping 61° to the south, and a normal‐oblique fault segment at the eastern termination of the rupture zone. The first fault segment ruptured the surface, while slip along the other two segments was confined to the lower sedimentary strata.
    Description: Published
    Description: 274-283
    Description: 2T. Deformazione crostale attiva
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 41
    Publication Date: 2022-08-31
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Fay, R., Hamel, S., van de Pol, M., Gaillard, J.-M., Yoccoz, N. G., Acker, P., Authier, M., Larue, B., Le Coeur, C., Macdonald, K. R., Nicol-Harper, A., Barbraud, C., Bonenfant, C., Van Vuren, D. H., Cam, E., Delord, K., Gamelon, M., Moiron, M., Pelletier, F., Rotella, J., Teplitsky, C., Visser, M. E., Wells, C. P., Wheelwright, N. T., Jenouvrier, S., & Saether, B.-E. Temporal correlations among demographic parameters are ubiquitous but highly variable across species. Ecology Letters, 25(7), (2022): 1640-1654, https://doi.org/10.1111/ele.14026.
    Description: Temporal correlations among demographic parameters can strongly influence population dynamics. Our empirical knowledge, however, is very limited regarding the direction and the magnitude of these correlations and how they vary among demographic parameters and species’ life histories. Here, we use long-term demographic data from 15 bird and mammal species with contrasting pace of life to quantify correlation patterns among five key demographic parameters: juvenile and adult survival, reproductive probability, reproductive success and productivity. Correlations among demographic parameters were ubiquitous, more frequently positive than negative, but strongly differed across species. Correlations did not markedly change along the slow-fast continuum of life histories, suggesting that they were more strongly driven by ecological than evolutionary factors. As positive temporal demographic correlations decrease the mean of the long-run population growth rate, the common practice of ignoring temporal correlations in population models could lead to the underestimation of extinction risks in most species.
    Description: This project was funded by the CNRS, including a long-term support by the OSU-OREME. Data collection for Weddell seals was supported by the National Science Foundation, Division of Polar Programs under grant number ANT-1640481 to J.J. Rotella, R.A. Garrott and D.B. Siniff and prior NSF Grants to R. A. Garrott, J. J. Rotella, D. B. Siniff and J. Ward Testa. Stéphanie Jenouvrier acknowledges the support of the NSF 1840058.
    Keywords: capture-recapture ; demographic correlation ; demography ; environmental stochasticity ; slow-fast continuum ; stochastic population dynamics ; temporal covariation
    Repository Name: Woods Hole Open Access Server
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  • 42
    Publication Date: 2022-10-27
    Description: This paper is not subject to U.S. copyright. The definitive version was published in ten Brink, U. S., Vanacore, E. A., Fielding, E. J., Chaytor, J. D., Lopez-Venegas, A. M., Baldwin, W. E., Foster, D. S., & Andrews, B. D. Mature diffuse tectonic block boundary revealed by the 2020 southwestern Puerto Rico seismic sequence. Tectonics, 41(3), (2022): e2021TC006896, https://doi.org/10.1029/2021TC006896.
    Description: Distributed faulting typically tends to coalesce into one or a few faults with repeated deformation. The progression of clustered medium-sized (≥Mw4.5) earthquakes during the 2020 seismic sequence in southwestern Puerto Rico (SWPR), modeling shoreline subsidence from InSAR, and sub-seafloor mapping by high-resolution seismic reflection profiles, suggest that the 2020 SWPR seismic sequence was distributed across several short intersecting strike-slip and normal faults beneath the insular shelf and upper slope of Guayanilla submarine canyon. Multibeam bathymetry map of the seafloor shows significant erosion and retreat of the shelf edge in the area of seismic activity as well as slope-parallel lineaments and submarine canyon meanders that typically develop over geological time. The T-axis of the moderate earthquakes further matches the extension direction previously measured on post early Pliocene (∼〉3 Ma) faults. We conclude that although similar deformation has likely taken place in this area during recent geologic time, it does not appear to have coalesced during this time. The deformation may represent the southernmost part of a diffuse boundary, the Western Puerto Rico Deformation Boundary, which accommodates differential movement between the Puerto Rico and Hispaniola arc blocks. This differential movement is possibly driven by the differential seismic coupling along the Puerto Rico—Hispaniola subduction zone. We propose that the compositional heterogeneity across the island arc retards the process of focusing the deformation into a single fault. Given the evidence presented here, we should not expect a single large event in this area but similar diffuse sequences in the future.
    Description: 2022-08-08
    Keywords: Rupture of multiple faults ; Intra-arc deformation ; Earthquake-generated submarine canyon ; Anisotropic arc composition ; Caribbean seismic hazard
    Repository Name: Woods Hole Open Access Server
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  • 43
    Publication Date: 2022-10-27
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Kuehn, E., Clausen, D. S., Null, R. W., Metzger, B. M., Willis, A. D., & Ozpolat, B. D. Segment number threshold determines juvenile onset of germline cluster expansion in Platynereis dumerilii. Journal of Experimental Zoology Part B: Molecular and Developmental Evolution, (2021.): 1-16, https://doi.org/10.1002/jez.b.23100.
    Description: Development of sexual characters and generation of gametes are tightly coupled with growth. Platynereis dumerilii is a marine annelid that has been used to study germline development and gametogenesis. P. dumerilii has germ cell clusters found across the body in the juvenile worms, and the clusters eventually form the gametes. Like other segmented worms, P. dumerilii grows by adding new segments at its posterior end. The number of segments reflect the growth state of the worms and therefore is a useful and measurable growth state metric to study the growth-reproduction crosstalk. To understand how growth correlates with progression of gametogenesis, we investigated germline development across several developmental stages. We discovered a distinct transition period when worms increase the number of germline clusters at a particular segment number threshold. Additionally, we found that keeping worms short in segment number, by manipulating environmental conditions or via amputations, supported a segment number threshold requirement for germline development. Finally, we asked if these clusters in P. dumerilii play a role in regeneration (as similar free-roaming cells are observed in Hydra and planarian regeneration) and found that the clusters were not required for regeneration in P. dumerilii, suggesting a strictly germline nature. Overall, these molecular analyses suggest a previously unidentified developmental transition dependent on the growth state of juvenile P. dumerilii leading to substantially increased germline expansion.
    Description: Research reported in this publication was supported by the National Institute of General Medical Sciences of the National Institutes of Health under Award Number R35GM138008 (to BDÖ) and R35GM133420 (to ADW) and Hibbitt Startup Funds (to BDÖ).
    Keywords: Annelida ; Critical size ; Developmental transition ; Gametogenesis ; Sexual reproduction
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  • 44
    Publication Date: 2022-10-27
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Donatelli, C., Kalra, T. S., Fagherazzi, S., Zhang, X., & Leonardi, N. Dynamics of marsh-derived sediments in lagoon-type estuaries. Journal of Geophysical Research: Earth Surface, 125(12), (2020): e2020JF005751, doi:10.1029/2020JF005751.
    Description: Salt marshes are valuable ecosystems that must trap sediments and accrete in order to counteract the deleterious effect of sea level rise. Previous studies have shown that the capacity of marshes to build up vertically depends on both autogenous and exogenous processes including ecogeomorphic feedbacks and sediment supply from in‐land and coastal ocean. There have been numerous efforts to quantify the role played by the sediments coming from marsh edge erosion on the resistance of salt marshes to sea level rise. However, the majority of existing studies investigating the interplay between lateral and vertical dynamics use simplified modeling approaches, and they do not consider that marsh retreat can affect the regional‐scale hydrodynamics and sediment retention in back‐barrier basins. In this study, we evaluated the fate of the sediments originating from marsh lateral loss by using high‐resolution numerical model simulations of Jamaica Bay, a small lagoonal estuary located in New York City. Our findings show that up to 42% of the sediment released during marsh edge erosion deposits on the shallow areas of the basin and over the vegetated marsh platforms, contributing positively to the sediment budget of the remaining salt marshes. Furthermore, we demonstrate that with the present‐day sediment supply from the ocean, the system cannot keep pace with sea level rise even accounting for the sediment liberated in the bay through marsh degradation. Our study highlights the relevance of multiple sediment sources for the maintenance of the marsh complex.
    Description: This study was supported by the Department of the Interior Hurricane Sandy Recovery program (ID G16AC00455, subaward to University of Liverpool). S. F. was partly supported by NSF awards 1637630 (PIE LTER) and 1832221 (VCR LTER). We thank Robert Chant from Rutgers University for sharing the hydrodynamic measurements in Jamaica Bay.
    Keywords: Marsh erosion ; Sediment recycling ; Sea level rise ; Jamaica Bay
    Repository Name: Woods Hole Open Access Server
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  • 45
    Publication Date: 2022-10-27
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ruppel, C. D., & Waite, W. F. Timescales and processes of methane hydrate formation and breakdown, with application to geologic systems. Journal of Geophysical Research: Solid Earth, 125(8), (2020): e2018JB016459, doi:10.1029/2018JB016459.
    Description: Gas hydrate is an ice‐like form of water and low molecular weight gas stable at temperatures of roughly −10°C to 25°C and pressures of ~3 to 30 MPa in geologic systems. Natural gas hydrates sequester an estimated one sixth of Earth's methane and are found primarily in deepwater marine sediments on continental margins, but also in permafrost areas and under continental ice sheets. When gas hydrate is removed from its stability field, its breakdown has implications for the global carbon cycle, ocean chemistry, marine geohazards, and interactions between the geosphere and the ocean‐atmosphere system. Gas hydrate breakdown can also be artificially driven as a component of studies assessing the resource potential of these deposits. Furthermore, geologic processes and perturbations to the ocean‐atmosphere system (e.g., warming temperatures) can cause not only dissociation, but also more widespread dissolution of hydrate or even formation of new hydrate in reservoirs. Linkages between gas hydrate and disparate aspects of Earth's near‐surface physical, chemical, and biological systems render an assessment of the rates and processes affecting the persistence of gas hydrate an appropriate Centennial Grand Challenge. This paper reviews the thermodynamic controls on methane hydrate stability and then describes the relative importance of kinetic, mass transfer, and heat transfer processes in the formation and breakdown (dissociation and dissolution) of gas hydrate. Results from numerical modeling, laboratory, and some field studies are used to summarize the rates of hydrate formation and breakdown, followed by an extensive treatment of hydrate dynamics in marine and cryospheric gas hydrate systems.
    Description: Both authors have received nearly two decades of support from the U.S. Geological Survey's (USGS's) Energy Resources Program and the Coastal/Marine Hazards and Resources Program and from numerous DOE‐USGS Interagency Agreements, most recently DE‐FE0023495. C. R. acknowledges support from NOAA's Office of Ocean Exploration and Research (OER) under NOAA‐USGS Interagency Agreement 16‐01118.
    Keywords: Gas hydrate ; Hydrate breakdown ; Hydrate formation ; Permafrost hydrate ; Geologic systems ; Marine hydrate
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  • 46
    Publication Date: 2022-10-27
    Description: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Biogeosciences 126(5), (2021): e2020JG006217, https://doi.org/10.1029/2020JG006217.
    Description: It is assumed that to treat excess NO3− high soil organic matter content (%OM) is required to maintain high denitrification rates in natural or restored wetlands. However, this excess also represents a risk by increasing soil decomposition rates triggering peat collapse and wetland fragmentation. Here, we evaluated the role of %OM and temperature interactions controlling denitrification rates in eroding (Barataria Bay-BLC) and emerging (Wax Lake Delta-WLD) deltaic regions in coastal Louisiana using the isotope pairing (IPT) and N2:Ar techniques. We also assessed differences between total (direct denitrification + coupled nitrification-denitrification) and net (total denitrification minus nitrogen fixation) denitrification rates in benthic and wetland habitats with contrasting %OM and bulk density (BD). Sediment (benthic) and soil (wetland) cores were collected during summer, spring, and winter (2015–2016) and incubated at close to in-situ temperatures (30°C, 20°C, and 10°C, respectively). Denitrification rates were linearly correlated with temperature; maximum mean rates ranged from 40.1–124.1 μmol m−2 h−1 in the summer with lower rates (〈26.2 ± 5.3 μmol m−2 h−1) in the winter seasons. Direct denitrification was higher than coupled denitrification in all seasons. Denitrification rates were higher in WLD despite lower %OM, lower total N concentration, and higher BD in wetland soils. Therefore, in environments with low carbon availability, high denitrification rates can be sustained as long as NO3− concentrations are high (〉30 μM) and water temperature is 〉10°C. In coastal Louisiana, substrates under these regimes are represented by emergent supra-tidal flats or land created by sediment diversions under oligohaline conditions (〈1 ppt).
    Description: This study was supported by the NOAA-Sea Grant Program-Louisiana (Grant 2013R/E-24) to Victor H. Rivera-Monroy and Kanchan Maiti. Victor H. Rivera-Monroy was also supported by the Department of the Interior South-Central Climate Adaptation Science Center (Cooperative Agreement #G12AC00002).
    Keywords: Coastal Louisiana ; Deltaic system ; Denitrification ; Nitrate loading ; Organic matter ; Seasonal change ; Sediment and freshwater diversions
    Repository Name: Woods Hole Open Access Server
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  • 47
    Publication Date: 2022-10-27
    Description: Author Posting. © American Geophysical Union, 2022. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 49(6), (2022): e2021GL095559, https://doi.org/10.1029/2021GL095559.
    Description: The valuable ecosystem services of salt marshes are spurring marsh restoration projects around the world. However, it is difficult to determine the final vegetated area based on physical drivers. Herein, we use a 3D fully coupled vegetation-hydrodynamic-morphological modeling system to simulate the final vegetation cover and the timescale to reach it under various forcing conditions. Marsh development in our simulations can be divided in three distinctive phases: A preparation phase characterized by sediment accumulation in the absence of vegetation, an encroachment phase in which the vegetated area grows, and an adjustment phase in which the vegetated area remains relatively constant while marsh accretes vertically to compensate for sea level rise. Sediment concentration, settling velocity, sea level rise, and tidal range each comparably affect equilibrium coverage and timescale in different ways. Our simulations show that the Unvegetated-Vegetated Ratio also relates to sediment budget in marsh development under most conditions.
    Description: This study was supported by the Department of the Interior Hurricane Sandy Recovery program (ID G16AC00455), NSF awards 1637630 (PIE LTER) and 1832221 (VCR LTER), and China Scholarship Council.
    Description: 2022-09-16
    Keywords: Marsh restoration ; Land reclamation ; COAWST ; Vegetation dynamics ; Phases of marsh development ; Expectance of marsh coverage
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  • 48
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Renfrew, I. A., Pickart, R. S., Vage, K., Moore, G. W. K., Bracegirdle, T. J., Elvidge, A. D., Jeansson, E., Lachlan-Cope, T., McRaven, L. T., Papritz, L., Reuder, J., Sodemann, H., Terpstra, A., Waterman, S., Valdimarsson, H., Weiss, A., Almansi, M., Bahr, F., Brakstad, A., Barrell, C., Brooke, J. K., Brooks, B. J., Brooks, I. M., Brooks, M. E., Bruvik, E. M., Duscha, C., Fer, I., Golid, H. M., Hallerstig, M., Hessevik, I., Huang, J., Houghton, L., Jonsson, S., Jonassen, M., Jackson, K., Kvalsund, K., Kolstad, E. W., Konstali, K., Kristiansen, J., Ladkin, R., Lin, P., Macrander, A., Mitchell, A., Olafsson, H., Pacini, A., Payne, C., Palmason, B., Perez-Hernandez, M. D., Peterson, A. K., Petersen, G. N., Pisareva, M. N., Pope, J. O., Seidl, A., Semper, S., Sergeev, D., Skjelsvik, S., Soiland, H., Smith, D., Spall, M. A., Spengler, T., Touzeau, A., Tupper, G., Weng, Y., Williams, K. D., Yang, X., & Zhou, S. The Iceland Greenland Seas Project. Bulletin of the American Meteorological Society, 100(9), (2019): 1795-1817, doi:10.1175/BAMS-D-18-0217.1.
    Description: The Iceland Greenland Seas Project (IGP) is a coordinated atmosphere–ocean research program investigating climate processes in the source region of the densest waters of the Atlantic meridional overturning circulation. During February and March 2018, a field campaign was executed over the Iceland and southern Greenland Seas that utilized a range of observing platforms to investigate critical processes in the region, including a research vessel, a research aircraft, moorings, sea gliders, floats, and a meteorological buoy. A remarkable feature of the field campaign was the highly coordinated deployment of the observing platforms, whereby the research vessel and aircraft tracks were planned in concert to allow simultaneous sampling of the atmosphere, the ocean, and their interactions. This joint planning was supported by tailor-made convection-permitting weather forecasts and novel diagnostics from an ensemble prediction system. The scientific aims of the IGP are to characterize the atmospheric forcing and the ocean response of coupled processes; in particular, cold-air outbreaks in the vicinity of the marginal ice zone and their triggering of oceanic heat loss, and the role of freshwater in the generation of dense water masses. The campaign observed the life cycle of a long-lasting cold-air outbreak over the Iceland Sea and the development of a cold-air outbreak over the Greenland Sea. Repeated profiling revealed the immediate impact on the ocean, while a comprehensive hydrographic survey provided a rare picture of these subpolar seas in winter. A joint atmosphere–ocean approach is also being used in the analysis phase, with coupled observational analysis and coordinated numerical modeling activities underway.
    Description: The IGP has received funding from the U.S. National Science Foundation: Grant OCE-1558742; the U.K.’s Natural Environment Research Council: AFIS (NE/N009754/1); the Research Council of Norway: MOCN (231647), VENTILATE (229791), SNOWPACE (262710) and FARLAB (245907); and the Bergen Research Foundation (BFS2016REK01). We thank all those involved in the field work associated with the IGP, particularly the officers and crew of the Alliance, and the operations staff of the aircraft campaign.
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  • 49
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Long, M. H., Rheuban, J. E., McCorkle, D. C., Burdige, D. J., & Zimmerman, R. C. Closing the oxygen mass balance in shallow coastal ecosystems. Limnology and Oceanography, 64(6), (2019): 2694-2708, doi: 10.1002/lno.11248.
    Description: The oxygen concentration in marine ecosystems is influenced by production and consumption in the water column and fluxes across both the atmosphere–water and benthic–water boundaries. Each of these fluxes has the potential to be significant in shallow ecosystems due to high fluxes and low water volumes. This study evaluated the contributions of these three fluxes to the oxygen budget in two contrasting ecosystems, a Zostera marina (eelgrass) meadow in Virginia, U.S.A., and a coral reef in Bermuda. Benthic oxygen fluxes were evaluated by eddy covariance. Water column oxygen production and consumption were measured using an automated water incubation system. Atmosphere–water oxygen fluxes were estimated by parameterizations based on wind speed or turbulent kinetic energy dissipation rates. We observed significant contributions of both benthic fluxes and water column processes to the oxygen mass balance, despite the often‐assumed dominance of the benthic communities. Water column rates accounted for 45% and 58% of the total oxygen rate, and benthic fluxes accounted for 23% and 39% of the total oxygen rate in the shallow (~ 1.5 m) eelgrass meadow and deeper (~ 7.5 m) reef site, respectively. Atmosphere–water fluxes were a minor component at the deeper reef site (3%) but a major component at the shallow eelgrass meadow (32%), driven by diel changes in the sign and strength of atmosphere–water gradient. When summed, the measured benthic, atmosphere–water, and water column rates predicted, with 85–90% confidence, the observed time rate of change of oxygen in the water column and provided an accurate, high temporal resolution closure of the oxygen mass balance.
    Description: This work was substantially improved by comments from two anonymous reviewers. We thank Victoria Hill, David Ruble, Jeremy Bleakney, and Brian Collister for assistance in the field and the staff of the Bermuda Institute of Ocean Sciences and the Anheuser‐Busch Coastal Research Center for logistical support. This work was supported by NSF OCE grants 1657727 (to M.H.L. and D.C.M.), 1635403 (to R.C.Z. and D.J.B.), and 1633951 (to M.H.L.).
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  • 50
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems XX (2019): Tyne, R. L., Barry, P. H., Hillegonds, D. J., Hunt, A. G., Kulongoski, J. T., Stephens, M. J., Byrne, D. J., & Ballentine, C. J. A novel method for the extraction, purification, and characterization of noble gases in produced fluids. Geochemistry Geophysics Geosystems, 20, (2019): 5588-5597, doi: 10.1029/2019GC008552.
    Description: Hydrocarbon systems with declining or viscous oil production are often stimulated using enhanced oil recovery (EOR) techniques, such as the injection of water, steam, and CO2, in order to increase oil and gas production. As EOR and other methods of enhancing production such as hydraulic fracturing have become more prevalent, environmental concerns about the impact of both new and historical hydrocarbon production on overlying shallow aquifers have increased. Noble gas isotopes are powerful tracers of subsurface fluid provenance and can be used to understand the impact of EOR on hydrocarbon systems and potentially overlying aquifers. In oil systems, produced fluids can consist of a mixture of oil, water and gas. Noble gases are typically measured in the gas phase; however, it is not always possible to collect gases and therefore produced fluids (which are water, oil, and gas mixtures) must be analyzed. We outline a new technique to separate and analyze noble gases in multiphase hydrocarbon‐associated fluid samples. An offline double capillary method has been developed to quantitatively isolate noble gases into a transfer vessel, while effectively removing all water, oil, and less volatile hydrocarbons. The gases are then cleaned and analyzed using standard techniques. Air‐saturated water reference materials (n = 24) were analyzed and results show a method reproducibility of 2.9% for 4He, 3.8% for 20Ne, 4.5% for 36Ar, 5 .3% for 84Kr, and 5.7% for 132Xe. This new technique was used to measure the noble gas isotopic compositions in six produced fluid samples from the Fruitvale Oil Field, Bakersfield, California.
    Description: This work was supported by a Natural Environment Research Council studentship to R. L. Tyne (grant NE/L002612/1) and the USGS (grant 15‐080‐250), as part of the California State Water Resource Control Board's, Oil and Gas Regional Groundwater Monitoring Program (RMP). Data can be accessed in Tables 1 and 2 and in the data release from Gannon et al. (2018). We thank the owners and operators at the Fruitvale Oil Field for access to wells. We thank Stuart Gilfillan and an anonymous reviewer for their constructive reviews as well as Marie Edmonds for editorial handling. We also thank Matthew Landon and Myles Moor from the USGS who provided helpful comments on an earlier version of the manuscript. Any use of trade, firm or product names are for descriptive purposes only and do not imply endorsement by the U.S. Government.
    Description: 2020-04-14
    Keywords: Noble Gas ; Methods ; Produced Fluids
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  • 51
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Chapman, A. S. A., Beaulieu, S. E., Colaco, A., Gebruk, A. V., Hilario, A., Kihara, T. C., Ramirez-Llodra, E., Sarrazin, J., Tunnicliffe, V., Amon, D. J., Baker, M. C., Boschen-Rose, R. E., Chen, C., Cooper, I. J., Copley, J. T., Corbari, L., Cordes, E. E., Cuvelier, D., Duperron, S., Du Preez, C., Gollner, S., Horton, T., Hourdez, S., Krylova, E. M., Linse, K., LokaBharathi, P. A., Marsh, L., Matabos, M., Mills, S. W., Mullineaux, L. S., Rapp, H. T., Reid, W. D. K., Rybakova (Goroslavskaya), E., Thomas, T. R. A., Southgate, S. J., Stohr, S., Turner, P. J., Watanabe, H. K., Yasuhara, M., & Bates, A. E. sFDvent: a global trait database for deep-sea hydrothermal-vent fauna. Global Ecology and Biogeography, 28(11), (2019): 1538-1551, doi: 10.1111/geb.12975.
    Description: Motivation Traits are increasingly being used to quantify global biodiversity patterns, with trait databases growing in size and number, across diverse taxa. Despite growing interest in a trait‐based approach to the biodiversity of the deep sea, where the impacts of human activities (including seabed mining) accelerate, there is no single repository for species traits for deep‐sea chemosynthesis‐based ecosystems, including hydrothermal vents. Using an international, collaborative approach, we have compiled the first global‐scale trait database for deep‐sea hydrothermal‐vent fauna – sFDvent (sDiv‐funded trait database for the Functional Diversity of vents). We formed a funded working group to select traits appropriate to: (a) capture the performance of vent species and their influence on ecosystem processes, and (b) compare trait‐based diversity in different ecosystems. Forty contributors, representing expertise across most known hydrothermal‐vent systems and taxa, scored species traits using online collaborative tools and shared workspaces. Here, we characterise the sFDvent database, describe our approach, and evaluate its scope. Finally, we compare the sFDvent database to similar databases from shallow‐marine and terrestrial ecosystems to highlight how the sFDvent database can inform cross‐ecosystem comparisons. We also make the sFDvent database publicly available online by assigning a persistent, unique DOI. Main types of variable contained Six hundred and forty‐six vent species names, associated location information (33 regions), and scores for 13 traits (in categories: community structure, generalist/specialist, geographic distribution, habitat use, life history, mobility, species associations, symbiont, and trophic structure). Contributor IDs, certainty scores, and references are also provided. Spatial location and grain Global coverage (grain size: ocean basin), spanning eight ocean basins, including vents on 12 mid‐ocean ridges and 6 back‐arc spreading centres. Time period and grain sFDvent includes information on deep‐sea vent species, and associated taxonomic updates, since they were first discovered in 1977. Time is not recorded. The database will be updated every 5 years. Major taxa and level of measurement Deep‐sea hydrothermal‐vent fauna with species‐level identification present or in progress. Software format .csv and MS Excel (.xlsx).
    Description: We would like to thank the following experts, who are not authors on this publication but made contributions to the sFDvent database: Anna Metaxas, Alexander Mironov, Jianwen Qiu (seep species contributions, to be added to a future version of the database) and Anders Warén. We would also like to thank Robert Cooke for his advice, time, and assistance in processing the raw data contributions to the sFDvent database using R. Thanks also to members of iDiv and its synthesis centre – sDiv – for much‐valued advice, support, and assistance during working‐group meetings: Doreen Brückner, Jes Hines, Borja Jiménez‐Alfaro, Ingolf Kühn and Marten Winter. We would also like to thank the following supporters of the database who contributed indirectly via early design meetings or members of their research groups: Malcolm Clark, Charles Fisher, Adrian Glover, Ashley Rowden and Cindy Lee Van Dover. Finally, thanks to the families of sFDvent working group members for their support while they were participating in meetings at iDiv in Germany. Financial support for sFDvent working group meetings was gratefully received from sDiv, the Synthesis Centre of iDiv (DFG FZT 118). ASAC was a PhD candidate funded by the SPITFIRE Doctoral Training Partnership (supported by the Natural Environmental Research Council, grant number: NE/L002531/1) and the University of Southampton at the time of submission. ASAC also thanks Dominic, Lesley, Lettice and Simon Chapman for their support throughout this project. AEB and VT are sponsored through the Canada Research Chair Programme. SEB received support from National Science Foundation Division of Environmental Biology Award #1558904 and The Joint Initiative Awards Fund from the Andrew W. Mellon Foundation. AC is supported by Program Investigador (IF/00029/2014/CP1230/CT0002) from Fundação para a Ciência e a Tecnologia (FCT). This study also had the support of Fundação para a Ciência e a Tecnologia, through the strategic project UID/MAR/04292/2013 granted to marine environmental sciences centre. Data compiled by AVG and EG were supported by Russian science foundation Grant 14‐50‐00095. AH was supported by the grant BPD/UI88/5805/2017 awarded by CESAM (UID/AMB/50017), which is financed by FCT/Ministério da Educação through national funds and co‐funded by fundo Europeu de desenvolvimento regional, within the PT2020 Partnership Agreement and Compete 2020. ERLL was partially supported by the MarMine project (247626/O30). JS was supported by Ifremer. Data on vent fauna from the East Scotia Ridge, Mid‐Cayman Spreading Centre, and Southwest Indian Ridge were obtained by UK natural environment research council Grants NE/D01249X/1, NE/F017774/1 and NE/H012087/1, respectively. REBR's contribution was supported by a Postdoctoral Fellowship at the University of Victoria, funded by the Canadian Healthy Oceans Network II Strategic Research Program (CHONe II). DC is supported by a post‐doctoral scholarship (SFRH/BPD/110278/2015) from FCT. HTR was supported by the Research Council of Norway through project number 70184227 and the KG Jebsen Centre for Deep Sea Research (University of Bergen). MY was partially supported by grants from the Research Grants Council of the Hong Kong Special Administrative Region, China (project codes: HKU 17306014, HKU 17311316).
    Keywords: biodiversity ; collaboration ; conservation ; cross‐ecosystem ; database ; deep sea ; functional trait ; global‐scale ; hydrothermal vent ; sFDvent
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  • 52
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 49(12), (2019): 3127-3143, doi: 10.1175/JPO-D-19-0011.1.
    Description: The Intermediate Western Boundary Current (IWBC) transports Antarctic Intermediate Water across the Vitória–Trindade Ridge (VTR), a seamount chain at ~20°S off Brazil. Recent studies suggest that the IWBC develops a strong cyclonic recirculation in Tubarão Bight, upstream of the VTR, with weak time dependency. We herein use new quasi-synoptic observations, data from the Argo array, and a regional numerical model to describe the structure and variability of the IWBC and to investigate its dynamics. Both shipboard acoustic Doppler current profiler (ADCP) data and trajectories of Argo floats confirm the existence of the IWBC recirculation, which is also captured by our Regional Oceanic Modeling System (ROMS) simulation. An “intermediate-layer” quasigeostrophic (QG) model indicates that the ROMS time-mean flow is a good proxy for the IWBC steady state, as revealed by largely parallel isolines of streamfunction ψ⎯ and potential vorticity Q⎯; a ψ⎯−Q⎯ scatter diagram also shows that the IWBC is potentially unstable. Further analysis of the ROMS simulation reveals that remotely generated, westward-propagating nonlinear eddies are the main source of variability in the region. These eddies enter the domain through the Tubarão Bight eastern edge and strongly interact with the IWBC. As they are advected downstream and negotiate the local topography, the eddies grow explosively through horizontal shear production.
    Description: We thank Frank O. Smith for copy editing and proofreading this manuscript. This study was financed in part by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—CAPES, Brazil—Finance Code 001 and by Projeto REMARSUL (Processo CAPES 88882.158621/2014-01), Projeto VT-Dyn (Processo FAPESP 2015/21729-4) and Projeto SUBMESO (Processo CNPq 442926/2015-4). Rocha was supported by a WHOI Postdoctoral Scholarship.
    Description: 2020-06-06
    Keywords: South Atlantic Ocean ; Instability ; Mesoscale processes ; Intermediate waters ; In situ oceanic observations ; Quasigeostrophic models
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  • 53
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Weber, L., González-Díaz, P., Armenteros, M., Ferrer, V. M., Bretos, F., Bartels, E., Santoro, A. E., & Apprill, A. Microbial signatures of protected and impacted Northern Caribbean reefs: changes from Cuba to the Florida Keys. Environmental Microbiology, 22(1), (2019): 499-519, doi: 10.1111/1462-2920.14870.
    Description: There are a few baseline reef‐systems available for understanding the microbiology of healthy coral reefs and their surrounding seawater. Here, we examined the seawater microbial ecology of 25 Northern Caribbean reefs varying in human impact and protection in Cuba and the Florida Keys, USA, by measuring nutrient concentrations, microbial abundances, and respiration rates as well as sequencing bacterial and archaeal amplicons and community functional genes. Overall, seawater microbial composition and biogeochemistry were influenced by reef location and hydrogeography. Seawater from the highly protected ‘crown jewel’ offshore reefs in Jardines de la Reina, Cuba had low concentrations of nutrients and organic carbon, abundant Prochlorococcus, and high microbial community alpha diversity. Seawater from the less protected system of Los Canarreos, Cuba had elevated microbial community beta‐diversity whereas waters from the most impacted nearshore reefs in the Florida Keys contained high organic carbon and nitrogen concentrations and potential microbial functions characteristic of microbialized reefs. Each reef system had distinct microbial signatures and within this context, we propose that the protection and offshore nature of Jardines de la Reina may preserve the oligotrophic paradigm and the metabolic dependence of the community on primary production by picocyanobacteria.
    Description: We thank Justin Ossolinski, Sean McNally, Tom Lankiewicz, Lázaro García, and the crew from R/V Felipe Poey for assistance with sample collection and processing. We thank Marlin Nauticas and Marinas for the use of their dive facilities. We thank Chris Wright, Mark Band, and staff at the University of Illinois W. M. Keck Center for Comparative and Functional Genomics for sequencing assistance, Karen Selph for training in flow cytometry, Krista Longnecker for TOC and TN analyses, and Joe Jennings for nutrient analyses. Funding was provided to A.A. and A.E.S. by a Dalio Explore award from the Dalio Foundation (now 'OceanX') and analysis time was supported with the NSF Graduate Research Fellowship award to L.W. and NSF award OCE 1736288 to A.A. Research was conducted under the LH112 AN (25) 2015 licence granted by the Cuban Center for Inspection and Environmental Control.
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  • 54
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Rheuban, J. E., Doney, S. C., McCorkle, D. C., & Jakuba, R. W. Quantifying the effects of nutrient enrichment and freshwater mixing on coastal ocean acidification. Journal of Geophysical Research-Oceans, 124, (2019): 9085-9100, doi: 10.1029/2019JC015556.
    Description: The U.S. Northeast is vulnerable to ocean and coastal acidification because of low alkalinity freshwater discharge that naturally acidifies the region, and high anthropogenic nutrient loads that lead to eutrophication in many estuaries. This study describes a combined nutrient and carbonate chemistry monitoring program in five embayments of Buzzards Bay, Massachusetts to quantify the effects of nutrient loading and freshwater discharge on aragonite saturation state (Ω). Monitoring occurred monthly from June 2015 to September 2017 with higher frequency at two embayments (Quissett and West Falmouth Harbors) and across nitrogen loading and freshwater discharge gradients. The more eutrophic stations experienced seasonal aragonite undersaturation, and at one site, nearly every measurement collected was undersaturated. We present an analytical framework to decompose variability in aragonite Ω into components driven by temperature, salinity, freshwater endmember mixing, and biogeochemical processes. We observed strong correlations between apparent oxygen utilization and the portion of aragonite Ω variation that we attribute to biogeochemistry. The regression slopes were consistent with Redfield ratios of dissolved inorganic carbon and total alkalinity to dissolved oxygen. Total nitrogen and the contribution of biogeochemical processes to aragonite Ω were highly correlated, and this relationship was used to estimate the likely effects of nitrogen loading improvements on aragonite Ω. Under nitrogen loading reduction scenarios, aragonite Ω in the most eutrophic estuaries could be raised by nearly 0.6 units, potentially increasing several stations above the critical threshold of 1. This analysis provides a quantitative framework for incorporating ocean and coastal acidification impacts into regulatory and management discussions.
    Description: We thank Kelly Luis, Michaela Fendrock, Will Oesterich, Sheron Luk, Marti Jeglinksi, and Tony Williams for their help with field sample collection and logistical support and Chris Neill, Lindsay Scott, Rich McHorney, and Paul Henderson for laboratory sample analysis. We also thank the Waquoit Bay National Estuarine Research Reserve for loaning their handheld water quality meters and two anonymous reviewers for their feedback on this manuscript. Financial support for this work was provided by the John D. and Catherine T. MacArthur Foundation (grant no. 14‐106159‐000‐CFP), MIT Sea Grant (subaward 5710004045) and the West Wind Foundation. The data used in this analysis can be found in the NOAA NCEI repository for carbonate chemistry measurements, the Ocean Carbon Data System at the following link: https://www.nodc.noaa.gov/ocads/data/0206206.xml.
    Keywords: Coastal Acidification ; Eutrophication
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  • 55
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Kwon, Y., Seo, H., Ummenhofer, C. C., & Joyce, T. M. Impact of multidecadal variability in Atlantic SST on winter atmospheric blocking. Journal of Climate, 33(3), (2020): 867-892, doi: 10.1175/JCLI-D-19-0324.1.
    Description: Recent studies have suggested that coherent multidecadal variability exists between North Atlantic atmospheric blocking frequency and the Atlantic multidecadal variability (AMV). However, the role of AMV in modulating blocking variability on multidecadal times scales is not fully understood. This study examines this issue primarily using the NOAA Twentieth Century Reanalysis for 1901–2010. The second mode of the empirical orthogonal function for winter (December–March) atmospheric blocking variability in the North Atlantic exhibits oppositely signed anomalies of blocking frequency over Greenland and the Azores. Furthermore, its principal component time series shows a dominant multidecadal variability lagging AMV by several years. Composite analyses show that this lag is due to the slow evolution of the AMV sea surface temperature (SST) anomalies, which is likely driven by the ocean circulation. Following the warm phase of AMV, the warm SST anomalies emerge in the western subpolar gyre over 3–7 years. The ocean–atmosphere interaction over these 3–7-yr periods is characterized by the damping of the warm SST anomalies by the surface heat flux anomalies, which in turn reduce the overall meridional gradient of the air temperature and thus weaken the meridional transient eddy heat flux in the lower troposphere. The anomalous transient eddy forcing then shifts the eddy-driven jet equatorward, resulting in enhanced Rossby wave breaking and blocking on the northern flank of the jet over Greenland. The opposite is true with the AMV cold phases but with much shorter lags, as the evolution of SST anomalies differs in the warm and cold phases.
    Description: We gratefully acknowledge support from the NSF Climate and Large-scale Dynamics Program (AGS-1355339) to Y-OK, HS, CCU, and TMJ, the NASA Physical Oceanography Program (NNX13AM59G) to Y-OK, HS, and TMJ, NOAA CPO Climate Variability and Predictability Program (NA13OAR4310139) and DOE CESD Regional and Global Model Analysis Program (DE-SC0019492) to Y-OK, and NSF Physical Oceanography Program (OCE-1419235) to HS. We are very grateful to the three anonymous reviewers and editor Dr. Mingfang Ting, for their thorough and insightful suggestions. The NOAA 20CR dataset was downloaded from the NOAA Earth System Research Laboratory Physical Science Division webpage (https://www.esrl.noaa.gov/psd/data/20thC_Rean/). Support for the 20CR Project version 2c dataset is provided by the U.S. Department of Energy, Office of Science Biological and Environmental Research (BER), and by the National Oceanic and Atmospheric Administration Climate Program Office. The HadISST dataset was downloaded from the U.K. Met Office Hadley Centre webpage (https://www.metoffice.gov.uk/hadobs/hadisst/). The ERA-20C dataset was downloaded from the ECMWF webpage (https://apps.ecmwf.int/datasets/data/era20c-daily/). The ERSST5 dataset was provided by the NOAA Earth System Research Laboratory Physical Science Division (https://www.esrl.noaa.gov/psd/data/gridded/data.noaa.ersst.v5.html).
    Keywords: North Atlantic Ocean ; Atmosphere-ocean interaction ; Blocking ; Climate variability ; Multidecadal variability ; North Atlantic Oscillation
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  • 56
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography and Paleoclimatology, 34, (2019): 2141-2157, doi: 10.1029/2019PA003731.
    Description: Dissolution of calcite in deep ocean sediments, which is required to balance global marine CaCO3 production and burial fluxes, is still a poorly understood process. In order to assess the mechanisms of dissolution in sediments, we analyzed four multicore tops taken along a depth transect on the Ontong‐Java Plateau. These cores were taken directly on the equator, and span water column calcite saturation states from ∼0.93 to ∼0.74, allowing us to assess the effect of dissolution on carbonate sediment composition. The top 2 cm of each multicore was sectioned and sieved to separate coccolith from foraminiferal calcite, and the %CaCO3, δ13C, Δ14C, and Mg/Ca were evaluated. The mass ratio of coccoliths to foraminifera increases by a factor of 3 as a function of water depth, reflecting the preferential dissolution of foraminifera. Carbon isotope (δ13C and Δ14C) data suggest that most dissolution takes place at the sediment‐water interface and primarily affects foraminifera. Mg/Ca analyses indicate that the Mg content of the entire foraminiferal assemblage decreases as a function of dissolution. In contrast, coccolith dissolution takes place within the sediments, rather than at the interface. Together these two processes cause coccoliths to be up to 1,000 radiocarbon years younger than foraminifera from the same depth horizon. Despite this within‐sediment coccolith dissolution flux, sediments below the calcite saturation horizon remain enriched in coccolith calcite. Combined with global seafloor hypsometry and calcium carbonate content, this enrichment suggests that globally, coccoliths may outweigh foraminifera in deep ocean sediments by a factor of 1.8.
    Description: A. V. S. thanks the NOSAMS facility and the WHOI/NOSAMS postdoc scholar program, James Funds, and the Bessette family for funding and support. A. Q. acknowledges Williams College research and travel funds. We thank the Stanley W. Watson Director's Discretionary Fund for the Picarro‐Automate analyzer. We thank Ellen Roosen at the WHOI core repository for help with sample identification and sectioning. Thanks to Gretchen Swarr and the WHOI plasma mass spectrometry facility. Finally, we thank Bill Martin and Wally Broecker for enlightening discussions on dissolution and radiocarbon dating of deep ocean sediments. All data are included as supporting information files and are archived with NOAA's World Data Service for Paleoceanography (WDS Paleo; https://www.ncdc.noaa.gov/paleo/study/28150).
    Description: 2020-05-15
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  • 57
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 47(1), (2020): e2019GL085378, doi:10.1029/2019GL085378.
    Description: Retrospectively comparing future model projections to observations provides a robust and independent test of model skill. Here we analyze the performance of climate models published between 1970 and 2007 in projecting future global mean surface temperature (GMST) changes. Models are compared to observations based on both the change in GMST over time and the change in GMST over the change in external forcing. The latter approach accounts for mismatches in model forcings, a potential source of error in model projections independent of the accuracy of model physics. We find that climate models published over the past five decades were skillful in predicting subsequent GMST changes, with most models examined showing warming consistent with observations, particularly when mismatches between model‐projected and observationally estimated forcings were taken into account.
    Description: Z. H. conceived the project, Z. H. and H. F. D. created the figures, and Z. H., H. F. D., T. A., and G. S. helped gather data and wrote the article text. A public GitHub repository with code used to analyze the data and generate figures and csv files containing the data shown in the figures is available online (https://github.com/hausfath/OldModels). Additional information on the code and data used in the analysis can be found in the supporting information. We would like to thank Piers Forster for providing the ensemble of observationally‐informed radiative forcing estimates. No dedicated funding from any of the authors supported this project.
    Description: 2020-06-04
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  • 58
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 50(2), (2020): 415-437, doi:10.1175/JPO-D-19-0019.1.
    Description: Results are presented from two dye release experiments conducted in the seasonal thermocline of the Sargasso Sea, one in a region of low horizontal strain rate (~10−6 s−1), the second in a region of intermediate horizontal strain rate (~10−5 s−1). Both experiments lasted ~6 days, covering spatial scales of 1–10 and 1–50 km for the low and intermediate strain rate regimes, respectively. Diapycnal diffusivities estimated from the two experiments were κz = (2–5) × 10−6 m2 s−1, while isopycnal diffusivities were κH = (0.2–3) m2 s−1, with the range in κH being less a reflection of site-to-site variability, and more due to uncertainties in the background strain rate acting on the patch combined with uncertain time dependence. The Site I (low strain) experiment exhibited minimal stretching, elongating to approximately 10 km over 6 days while maintaining a width of ~5 km, and with a notable vertical tilt in the meridional direction. By contrast, the Site II (intermediate strain) experiment exhibited significant stretching, elongating to more than 50 km in length and advecting more than 150 km while still maintaining a width of order 3–5 km. Early surveys from both experiments showed patchy distributions indicative of small-scale stirring at scales of order a few hundred meters. Later surveys show relatively smooth, coherent distributions with only occasional patchiness, suggestive of a diffusive rather than stirring process at the scales of the now larger patches. Together the two experiments provide important clues as to the rates and underlying processes driving diapycnal and isopycnal mixing at these scales.
    Description: Results are presented from two dye release experiments conducted in the seasonal thermocline of the Sargasso Sea, one in a region of low horizontal strain rate (~10−6 s−1), the second in a region of intermediate horizontal strain rate (~10−5 s−1). Both experiments lasted ~6 days, covering spatial scales of 1–10 and 1–50 km for the low and intermediate strain rate regimes, respectively. Diapycnal diffusivities estimated from the two experiments were κz = (2–5) × 10−6 m2 s−1, while isopycnal diffusivities were κH = (0.2–3) m2 s−1, with the range in κH being less a reflection of site-to-site variability, and more due to uncertainties in the background strain rate acting on the patch combined with uncertain time dependence. The Site I (low strain) experiment exhibited minimal stretching, elongating to approximately 10 km over 6 days while maintaining a width of ~5 km, and with a notable vertical tilt in the meridional direction. By contrast, the Site II (intermediate strain) experiment exhibited significant stretching, elongating to more than 50 km in length and advecting more than 150 km while still maintaining a width of order 3–5 km. Early surveys from both experiments showed patchy distributions indicative of small-scale stirring at scales of order a few hundred meters. Later surveys show relatively smooth, coherent distributions with only occasional patchiness, suggestive of a diffusive rather than stirring process at the scales of the now larger patches. Together the two experiments provide important clues as to the rates and underlying processes driving diapycnal and isopycnal mixing at these scales.
    Description: 2020-08-06
    Keywords: Ocean ; Atlantic Ocean ; Diapycnal mixing ; Diffusion ; Dispersion ; Mixing
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  • 59
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Liang, Y., Kwon, Y., Frankignoul, C., Danabasoglu, G., Yeager, S., Cherchi, A., Gao, Y., Gastineau, G., Ghosh, R., Matei, D., Mecking, J., V., Peano, D., Suo, L., & Tian, T. Quantification of the arctic sea ice-driven atmospheric circulation variability in coordinated large ensemble simulations. Geophysical Research Letters, 47(1), (2020): e2019GL085397, doi:10.1029/2019GL085397.
    Description: A coordinated set of large ensemble atmosphere‐only simulations is used to investigate the impacts of observed Arctic sea ice‐driven variability (SIDV) on the atmospheric circulation during 1979–2014. The experimental protocol permits separating Arctic SIDV from internal variability and variability driven by other forcings including sea surface temperature and greenhouse gases. The geographic pattern of SIDV is consistent across seven participating models, but its magnitude strongly depends on ensemble size. Based on 130 members, winter SIDV is ~0.18 hPa2 for Arctic‐averaged sea level pressure (~1.5% of the total variance), and ~0.35 K2 for surface air temperature (~21%) at interannual and longer timescales. The results suggest that more than 100 (40) members are needed to separate Arctic SIDV from other components for dynamical (thermodynamical) variables, and insufficient ensemble size always leads to overestimation of SIDV. Nevertheless, SIDV is 0.75–1.5 times as large as the variability driven by other forcings over northern Eurasia and Arctic.
    Description: The authors thank Editor Christina Patricola and two anonymous reviewers for their comprehensive and insightful comments, which have led to improved presentation of this manuscript. We acknowledge support by the Blue‐Action Project (European Union's Horizon 2020 research and innovation program, 727852, http://www.blue‐action.eu/index.php?id = 3498). The WHOI‐NCAR group is also supported by the US National Science Foundation (NSF) Office of Polar Programs Grants 1736738 and 1737377, and their computing and data storage resources, including the Cheyenne supercomputer (doi:10.5065/D6RX99HX), were provided by the Computational and Information Systems Laboratory at NCAR. NCAR is a major facility sponsored by the U.S. NSF under Cooperative Agreement 1852977. The LOCEAN‐IPSL group was granted access to the HPC resources of TGCC under the Allocation A5‐017403 made by GENCI. The SST and SIC data were downloaded from the U.K. Met Office Hadley Centre Observations Datasets (http://www.metoffice.gov.uk/hadobs/hadisst).
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  • 60
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 21(2), (2020): e2019GC008414, doi:10.1029/2019GC008414.
    Description: X‐ray fluorescence (XRF) core scanning of marine and lake sediments has been extensively used to study changes in past environmental and climatic processes over a range of timescales. The interpretation of XRF‐derived element ratios in paleoclimatic and paleoceanographic studies primarily considers differences in the relative abundances of particular elements. Here we present new XRF core scanning data from two long sediment cores in the Andaman Sea in the northern Indian Ocean and show that sea level related processes influence terrigenous inputs based proxies such as Ti/Ca, Fe/Ca, and elemental concentrations of the transition metals (e.g., Mn). Zr/Rb ratios are mainly a function of changes in median grain size of lithogenic particles and often covary with changes in Ca concentrations that reflect changes in biogenic calcium carbonate production. This suggests that a common process (i.e., sea level) influences both records. The interpretation of lighter element data (e.g., Si and Al) based on low XRF counts is complicated as variations in mean grain size and water content result in systematic artifacts and signal intensities not related to the Al or Si content of the sediments. This highlights the need for calibration of XRF core scanning data based on discrete sample analyses and careful examination of sediment properties such as porosity/water content for reliably disentangling environmental signals from other physical properties. In the case of the Andaman Sea, reliable extraction of a monsoon signal requires accounting for the sea level influence on the XRF data.
    Description: The staff at the Bremen Core Repository is thanked for their help with core handling and Sam Müller at the University of Kiel provided technical assistance with the XRF scanner. We thank two anonymous reviewers for their insightful comments that improved the manuscript significantly. This work was partially funded through DFG Grant HA 5751/3. P. A. and K. N.‐K. acknowledge support from UK‐IODP and Natural and Environment Research Council, UK. The authors express their thanks to all those who contributed to the success of the National Gas Hydrate Program Expedition 01 (NGHP01) and Expedition 353. The data set supporting the conclusions of this article is available in the PANGEA repository (doi: https://doi.pangaea.de/10.1594/PANGAEA.910533).
    Description: 2020-07-10
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  • 61
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of the Atmospheric and Oceanic Technology 37(5), (2020): 789-806, doi:10.1175/JTECH-D-18-0244.1.
    Description: Realistic ocean state prediction and its validation rely on the availability of high quality in situ observations. To detect data errors, adequate quality check procedures must be designed. This paper presents procedures that take advantage of the ever-growing observation databases that provide climatological knowledge of the ocean variability in the neighborhood of an observation location. Local validity intervals are used to estimate binarily whether the observed values are considered as good or erroneous. Whereas a classical approach estimates validity bounds from first- and second-order moments of the climatological parameter distribution, that is, mean and variance, this work proposes to infer them directly from minimum and maximum observed values. Such an approach avoids any assumption of the parameter distribution such as unimodality, symmetry around the mean, peakedness, or homogeneous distribution tail height relative to distribution peak. To reach adequate statistical robustness, an extensive manual quality control of the reference dataset is critical. Once the data have been quality checked, the local minima and maxima reference fields are derived and the method is compared with the classical mean/variance-based approach. Performance is assessed in terms of statistics of good and bad detections. It is shown that the present size of the reference datasets allows the parameter estimates to reach a satisfactory robustness level to always make the method more efficient than the classical one. As expected, insufficient robustness persists in areas with an especially low number of samples and high variability.
    Description: This study has been conducted using EU Copernicus Marine Service Information and was supported by the European Union within the EU Copernicus Marine Service In Situ phase-I and phase-II contracts led by Ifremer. The publication was also supported by SOERE CTDO2 in France. The Argo data were collected and made freely available by the International Argo Program and the national programs that contribute to it (see http://www.argo.ucsd.edu, http://argo.jcommops.org). The Argo Program is part of the Global Ocean Observing System (http://doi.org/10.17882/42182). The marine mammal data were collected and made freely available by the International MEOP Consortium and the national programs that contribute to it (see http://www.meop.net; https://doi.org/10.17882/45461). Aleix Gelabert and Dídac Costa were the skippers of the OPOO, sponsored by the Intergovernmental Oceanographic Commission (UNESCO) and Pharmaton. The BWR is a periodic oceanic race organized by the Fundació Navegació Oceànica de Barcelona (FNOB). Reviewer D. Briand provided some useful comments on the final version of the draft paper before submission.
    Description: 2020-11-04
    Keywords: Ocean ; Climatology ; Salinity ; Temperature ; Data quality control ; Oceanic variability
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  • 62
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 125(4), (2020): e2019JC015470, doi:10.1029/2019JC015470.
    Description: This study is to quantify the effects of mesoscale eddies on air‐sea heat fluxes and related air‐sea variables in the South China Sea. Using satellite observations of sea surface temperature (SST) and sea surface height anomaly and a high‐resolution air‐sea heat flux product for the 16‐year period from 2000 to 2015, we conducted the composite patterns of air‐sea fluxes and variables associated with anticyclonic eddies (AEs) and cyclonic eddies (CEs). It is found that the SST‐sea surface height correlations over eddies are not always positive. Only 56% of AEs are corresponded with positive SST anomalies (SSTA), that is, SST+ AEs, and 58% of CEs with negative SSTA, that is, SST− CEs. The percentage of these eddies increases with eddy amplitude and shows slight seasonal variations, higher in winter and lower in summer. Composites of SSTA, air‐sea variables, and fluxes are constructed over all eddies, including both SST+ eddies and SST− eddies. All composites show asymmetric patterns, showing that the centers (where the extrema are located) of the fluxes and variables shift westward and poleward (equatorward) relative to the AEs (CEs) cores. Besides, composites of latent heat flux (LHF), sensible heat flux (SHF), and air temperature show monopole patterns, while composites of wind speed and specific humidity show dipole patterns. For SST+ AEs, the coupling strength is 39.6 ± 6.5 W/m2 (7.2 ± 1.7 W/m2) per degree increase of SSTA for LHF (SHF). For SST− CEs, the coupling strength is 39.0 ± 2.0 W/m2 (9.0 ± 0.96 W/m2) per degree decrease of SSTA for LHF (SHF).
    Description: This research was conducted while Y. Liu was a visiting graduate student at Woods Hole Oceanographic Institution (WHOI). She sincerely thanks the WHOI Academic Programs Office for hosting her visit and is grateful to the support from China Scholarship Council (CSC). This study was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant XDA19060101), the Key R & D project of Shandong Province (Grant 2019JZZY010102), the Key deployment project of Center for Ocean Mega‐Science, CAS (Grant COMS2019R02), the CAS Program (Grant Y9KY04101L), and the National Natural Science Foundation of China (Grant 41776183 and 41906157). Dr. Xiangze Jin is acknowledged for providing the OAFluxHR analysis and for his programming support and guidance to this study. Heat flux data used in this paper can be downloaded (from https://figshare.com/articles/Eddy‐induced_heat_flux_in_the_South_China_Sea/11949735). AVISO SSH data are downloaded from the website (http://www.aviso.altimetry.fr), OISST from the ftp://eclipse.ncdc.noaa.gov/ site, and OAFluxHR analysis will be available from the project website (http://oaflux.whoi.edu).
    Description: 2020-09-16
    Keywords: mesoscale eddies ; air‐sea coupling ; South China Sea
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  • 63
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 50(5), (2020): 1245-1263, doi:10.1175/JPO-D-19-0213.1.
    Description: We use laboratory experiments and theoretical modeling to investigate the surface expression of a subglacial discharge plume, as occurs at many fjords around Greenland. The experiments consider a fountain that is released vertically into a homogeneous fluid, adjacent either to a vertical or a sloping wall, that then spreads horizontally at the free surface before sinking back to the bottom. We present a model that separates the fountain into two separate regions: a vertical fountain and a horizontal, negatively buoyant jet. The model is compared to laboratory experiments that are conducted over a range of volume fluxes, density differences, and ambient fluid depths. It is shown that the nondimensionalized length, width, and aspect ratio of the surface expression are dependent on the Froude number, calculated at the start of the negatively buoyant jet. The model is applied to observations of the surface expression from a Greenland subglacial discharge plume. In the case where the discharge plume reaches the surface with negative buoyancy the model can be used to estimate the discharge properties at the base of the glacier.
    Description: We gratefully acknowledge technical assistance from Anders Jensen and thank anonymous reviewers for improving the clarity of the manuscript. CM thanks the Weston Howard Jr. Scholarship for funding. Support to CC was given by NSF project OCE-1434041 and OCE-1658079.
    Description: 2020-10-27
    Keywords: Ocean ; Glaciers ; Ice sheets ; Convection ; Laboratory/physical models
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  • 64
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 50(3), (2020): 679-694, doi:10.1175/JPO-D-19-0218.1.
    Description: The zonally integrated flow in a basin can be separated into the divergent/nondivergent parts, and a uniquely defined meridional overturning circulation (MOC) can be calculated. For a basin with significant volume exchange at zonal open boundaries, this method is competent in removing the components associated with the nonzero source terms due to zonal transports at open boundaries. This method was applied to the zonally integrated flow in the Indian Ocean basin extended all the way to the Antarctic by virtue of the ECCO dataset. The contributions due to two major zonal flow systems at open boundaries, the Indonesian Throughflow (ITF) and the Antarctic Circumpolar Current (ACC), were well separated from the rotational flow component, and a nondivergent overturning circulation pattern was identified. Comparisons with previous studies on the MOC of the Indian Ocean in different seasons showed overall consistency but with refinements in details to the south of the entry of the ITF, reflecting the influence of ITF on the MOC pattern in the domain. Other options of decomposition are also examined.
    Description: LH was supported by the National Basic Research Program of China through Grant 2019YFA0606703 and “The Fundamental Research Funds of Shandong University” (2019GN051). The authors thank the anonymous reviewers and the editor for their constructive comments. Code availability: The Matlab code that performs the decomposition and produces some figures in this paper is available at https://github.com/lei-han-SDU/IMOC/.
    Description: 2020-09-02
    Keywords: Meridional overturning circulation ; Ocean circulation ; Streamfunction
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  • 65
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Staudinger, M. D., Goyert, H., Suca, J. J., Coleman, K., Welch, L., Llopiz, J. K., Wiley, D., Altman, I., Applegate, A., Auster, P., Baumann, H., Beaty, J., Boelke, D., Kaufman, L., Loring, P., Moxley, J., Paton, S., Powers, K., Richardson, D., Robbins, J., Runge, J., Smith, B., Spiegel, C., & Steinmetz, H. The role of sand lances (Ammodytes sp.) in the Northwest Atlantic ecosystem: a synthesis of current knowledge with implications for conservation and management. Fish and Fisheries, 00, (2020): 1-34, doi:10.1111/faf.12445.
    Description: The American sand lance (Ammodytes americanus, Ammodytidae) and the Northern sand lance (A. dubius, Ammodytidae) are small forage fishes that play an important functional role in the Northwest Atlantic Ocean (NWA). The NWA is a highly dynamic ecosystem currently facing increased risks from climate change, fishing and energy development. We need a better understanding of the biology, population dynamics and ecosystem role of Ammodytes to inform relevant management, climate adaptation and conservation efforts. To meet this need, we synthesized available data on the (a) life history, behaviour and distribution; (b) trophic ecology; (c) threats and vulnerabilities; and (d) ecosystem services role of Ammodytes in the NWA. Overall, 72 regional predators including 45 species of fishes, two squids, 16 seabirds and nine marine mammals were found to consume Ammodytes. Priority research needs identified during this effort include basic information on the patterns and drivers in abundance and distribution of Ammodytes, improved assessments of reproductive biology schedules and investigations of regional sensitivity and resilience to climate change, fishing and habitat disturbance. Food web studies are also needed to evaluate trophic linkages and to assess the consequences of inconsistent zooplankton prey and predator fields on energy flow within the NWA ecosystem. Synthesis results represent the first comprehensive assessment of Ammodytes in the NWA and are intended to inform new research and support regional ecosystem‐based management approaches.
    Description: This manuscript is the result of follow‐up work stemming from a working group formed at a two‐day multidisciplinary and international workshop held at the Parker River National Wildlife Refuge, Massachusetts in May 2017, which convened 55 experts scientists, natural resource managers and conservation practitioners from 15 state, federal, academic and non‐governmental organizations with interest and expertise in Ammodytes ecology. Support for this effort was provided by USFWS, NOAA Stellwagen Bank National Marine Sanctuary, U.S. Department of the Interior, U.S. Geological Survey, Northeast Climate Adaptation Science Center (Award # G16AC00237), an NSF Graduate Research Fellowship to J.J.S., a CINAR Fellow Award to J.K.L. under Cooperative Agreement NA14OAR4320158, NSF award OCE‐1325451 to J.K.L., NSF award OCE‐1459087 to J.A.R, a Regional Sea Grant award to H.B. (RNE16‐CTHCE‐l), a National Marine Sanctuary Foundation award to P.J.A. (18‐08‐B‐196) and grants from the Mudge Foundation. The contents of this paper are the responsibility of the authors and do not necessarily represent the views of the National Oceanographic and Atmospheric Administration, U.S. Fish and Wildlife Service, New England Fishery Management Council and Mid‐Atlantic Fishery Management Council. This manuscript is submitted for publication with the understanding that the United States Government is authorized to reproduce and distribute reprints for Governmental purposes. Any use of trade, firm or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
    Keywords: Ammodytes ; ecosystem‐based management ; forage fish ; life history ; sand lance ; trophic ecology
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  • 66
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 125(5), (2020): e2019JC015348, doi:10.1029/2019JC015348.
    Description: Here we present an assessment of eddy activity in a 3,500 × 2,000 km region of the North Pacific. Eddies were identified and tracked within a numerical simulation that used the Massachusetts Institute of Technology general circulation model and an eddy characterization algorithm. Spatially, eddy births were more frequent: (1) nearshore (cyclones) and offshore (anticyclones) on the windward side of the main Hawai‘ian Islands; (2) in patches of cyclones and anticyclones that resembled the dipole structure of wind stress curl along the islands’ leeward side; and (3) in zonal patches of eddies of both polarities west and north of the islands. Temporally, high eddy activities occurred in spring. There was a meridional distribution of eddy lifespans, which increased northward. Cyclones were more abundant, longer‐lived, smaller, and more nonlinear. Reef fish spawning locations in Hawai‘i coincide with the regions of high eddy activity, with nonlinear eddies responsible for high larval retention.
    Description: This work was supported by the National Ocean and Atmospheric Administration (NOAA) Fisheries And The Environment (FATE) Award WE133F17SE1020. This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by the National Science Foundation Grant NSF‐OCE170005.
    Description: 2020-10-29
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  • 67
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 47(15), (2020): e2020GL089135, doi:10.1029/2020GL089135.
    Description: Convection penetrates to the ocean bottom in the North Atlantic but not in the North Pacific. This study examines the role of basin width in shutting down high‐latitude ocean convection. Deep convection is triggered by polar cooling, but it is opposed by precipitation. A two‐layer analytical model illustrates that the overturning circulation acts to mitigate the effect of precipitation by advecting salty, dense water from subtropical latitudes to polar latitudes. The nonlinear dependence of the overturning strength on basin width makes it more efficient in a narrow basin, resulting in a convection shutdown at a stronger freshwater forcing. These predictions are confirmed by simulations with a general circulation model configured with a single closed basin to the north and a reentrant channel to the south. This suggests that basin width may play a role in suppressing convection in the North Pacific but not in the North Atlantic.
    Description: M. K. Y. and R. F. acknowledge support through National Science Foundation (NSF) Awards OCE‐1536515 and AGS‐1835576. M. K. Y. acknowledges funding from the National Defense Science and Engineering Graduate Fellowship and the American Meteorological Society Graduate Student Fellowship. G. R. F. was supported by NSF OCE‐1459702.
    Description: 2020-01-2021
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  • 68
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    American Meteorological Society
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 50(9), (2020): 2491-2506, doi:10.1175/JPO-D-20-0056.1.
    Description: An idealized two-layer shallow water model is applied to the study of the dynamics of the Arctic Ocean halocline. The model is forced by a surface stress distribution reflective of the observed wind stress pattern and ice motion and by an inflow representing the flow of Pacific Water through Bering Strait. The model reproduces the main elements of the halocline circulation: an anticyclonic Beaufort Gyre in the western basin (representing the Canada Basin), a cyclonic circulation in the eastern basin (representing the Eurasian Basin), and a Transpolar Drift between the two gyres directed from the upwind side of the basin to the downwind side of the basin. Analysis of the potential vorticity budget shows a basin-averaged balance primarily between potential vorticity input at the surface and dissipation at the lateral boundaries. However, advection is a leading-order term not only within the anticyclonic and cyclonic gyres but also between the gyres. This means that the eastern and western basins are dynamically connected through the advection of potential vorticity. Both eddy and mean fluxes play a role in connecting the regions of potential vorticity input at the surface with the opposite gyre and with the viscous boundary layers. These conclusions are based on a series of model runs in which forcing, topography, straits, and the Coriolis parameter were varied.
    Description: This study was supported by National Science Foundation Grant OPP-1822334. Comments and suggestions from two anonymous referees greatly helped to improve the paper.
    Description: 2021-02-17
    Keywords: Eddies ; Ekman pumping/transport ; Ocean circulation ; Ocean dynamics ; Potential vorticity ; Shallow-water equations
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  • 69
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society 101(6), (2020): E897-E904, doi:10.1175/BAMS-D-19-0047.1.
    Description: Over the past 15 years, numerous studies have suggested that the sinking branches of Earth’s Hadley circulation and the associated subtropical dry zones have shifted poleward over the late twentieth century and early twenty-first century. Early estimates of this tropical widening from satellite observations and reanalyses varied from 0.25° to 3° latitude per decade, while estimates from global climate models show widening at the lower end of the observed range. In 2016, two working groups, the U.S. Climate Variability and Predictability (CLIVAR) working group on the Changing Width of the Tropical Belt and the International Space Science Institute (ISSI) Tropical Width Diagnostics Intercomparison Project, were formed to synthesize current understanding of the magnitude, causes, and impacts of the recent tropical widening evident in observations. These working groups concluded that the large rates of observed tropical widening noted by earlier studies resulted from their use of metrics that poorly capture changes in the Hadley circulation, or from the use of reanalyses that contained spurious trends. Accounting for these issues reduces the range of observed expansion rates to 0.25°–0.5° latitude decade‒1—within the range from model simulations. Models indicate that most of the recent Northern Hemisphere tropical widening is consistent with natural variability, whereas increasing greenhouse gases and decreasing stratospheric ozone likely played an important role in Southern Hemisphere widening. Whatever the cause or rate of expansion, understanding the regional impacts of tropical widening requires additional work, as different forcings can produce different regional patterns of widening.
    Description: We thank U.S. CLIVAR and ISSI for funding the two working groups. We thank all members of the working groups for helpful discussions, and the U.S. CLIVAR and ISSI offices and their sponsoring agencies (NASA, NOAA, NSF, DOE, ESA, Swiss Confederation, Swiss Academy of Sciences, and University of Bern) for supporting these groups and activities.
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  • 70
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 50(4), (2020): 887-905, doi:10.1175/JPO-D-19-0110.1.
    Description: The Equatorial Undercurrent (EUC) encounters the Galápagos Archipelago on the equator as it flows eastward across the Pacific. The impact of the Galápagos Archipelago on the EUC in the eastern equatorial Pacific remains largely unknown. In this study, the path of the EUC as it reaches the Galápagos Archipelago is measured directly using high-resolution observations obtained by autonomous underwater gliders. Gliders were deployed along three lines that define a closed region with the Galápagos Archipelago as the eastern boundary and 93°W from 2°S to 2°N as the western boundary. Twelve transects were simultaneously occupied along the three lines during 52 days in April–May 2016. Analysis of individual glider transects and average sections along each line show that the EUC splits around the Galápagos Archipelago. Velocity normal to the transects is used to estimate net horizontal volume transport into the volume. Downward integration of the net horizontal transport profile provides an estimate of the time- and areal-averaged vertical velocity profile over the 52-day time period. Local maxima in vertical velocity occur at depths of 25 and 280 m with magnitudes of (1.7 ± 0.6) × 10−5 m s−1 and (8.0 ± 1.6) × 10−5 m s−1, respectively. Volume transport as a function of salinity indicates that water crossing 93°W south (north) of 0.4°S tends to flow around the south (north) side of the Galápagos Archipelago. Comparisons are made between previous observational and modeling studies with differences attributed to effects of the strong 2015/16 El Niño event, the annual cycle of local winds, and varying longitudes between studies of the equatorial Pacific.
    Description: This work was supported by National Science Foundation (Grants OCE-1232971 and OCE-1233282) and the NASA Earth and Space Science Fellowship Program (Grant 80NSSC17K0443).
    Keywords: Tropics ; Boundary currents ; Topographic effects ; Transport ; Upwelling/downwelling ; In situ oceanic observations
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  • 71
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 50(10), (2020): 2849-2871, https://doi.org/10.1175/JPO-D-20-0086.1.
    Description: The structure, transport, and seasonal variability of the West Greenland boundary current system near Cape Farewell are investigated using a high-resolution mooring array deployed from 2014 to 2018. The boundary current system is comprised of three components: the West Greenland Coastal Current, which advects cold and fresh Upper Polar Water (UPW); the West Greenland Current, which transports warm and salty Irminger Water (IW) along the upper slope and UPW at the surface; and the Deep Western Boundary Current, which advects dense overflow waters. Labrador Sea Water (LSW) is prevalent at the seaward side of the array within an offshore recirculation gyre and at the base of the West Greenland Current. The 4-yr mean transport of the full boundary current system is 31.1 ± 7.4 Sv (1 Sv ≡ 106 m3 s−1), with no clear seasonal signal. However, the individual water mass components exhibit seasonal cycles in hydrographic properties and transport. LSW penetrates the boundary current locally, through entrainment/mixing from the adjacent recirculation gyre, and also enters the current upstream in the Irminger Sea. IW is modified through air–sea interaction during winter along the length of its trajectory around the Irminger Sea, which converts some of the water to LSW. This, together with the seasonal increase in LSW entering the current, results in an anticorrelation in transport between these two water masses. The seasonality in UPW transport can be explained by remote wind forcing and subsequent adjustment via coastal trapped waves. Our results provide the first quantitatively robust observational description of the boundary current in the eastern Labrador Sea.
    Description: A.P., R.S.P., F.B., D.J.T., and A.L.R. were funded by Grants OCE-1259618 and OCE-1756361 from the National Science Foundation. I.L.B, F.S., and J.H. were supported by U.S. National Science Foundation Grants OCE-1258823 and OCE-1756272. Mooring data from MA2 was funded by the European Union 7th Framework Programme (FP7 2007-2013) under Grant 308299 (NACLIM) and the Horizon 2020 research and innovation program under Grant 727852 (Blue-Action). J.K. and M.O. acknowledge EU Horizon 2020 funding Grants 727852 (Blue-action) and 862626 (EuroSea) and from the German Ministry of Research and Education (RACE Program). G.W.K.M. acknowledges funding from the Natural Sciences and Engineering Research Council.
    Keywords: Boundary currents ; Convection ; Deep convection ; Transport ; In situ oceanic observations ; Seasonal cycle
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  • 72
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society 101(11), (2020): E1996-E2004, https://doi.org/10.1175/BAMS-D-19-0305.1.
    Description: A long-standing challenge in oceanography is the observing, modeling, and prediction of vertical transport, which links the sunlit and atmospherically mediated surface boundary layer with the deeper ocean. Vertical motions play a critical role in the exchange of heat, freshwater, and biogeochemical tracers between the surface and the ocean interior. The most intense vertical velocities occur at horizontal scales less than 10 km, making them difficult to observe in the ocean and to resolve in models. Understanding how finescale turbulent motions and 0.1–10 km submesoscale processes contribute to the large-scale budgets of nutrients, oxygen, carbon, and heat and affect sea surface temperature, the air–sea exchange of gases, and the carbon cycle is one of the key challenges in oceanography.
    Description: CALYPSO is a Departmental Research Initiative (DRI) funded by the U.S. Office of Naval Research (ONR). It is a collaborative program involving more than 30 scientists and students and multiple institutions in the United States, Spain, and Italy. Measurements were conducted from the NRV Alliance, Pourquoi Pas?, and SOCIB. We are grateful to the captains and crews of these research vessels and the technical and scientific staff involved in making measurements, running models, analyzing data, and providing support.
    Description: 2021-05-01
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  • 73
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Schultz, C., Doney, S. C., Zhang, W. G., Regan, H., Holland, P., Meredith, M. P., & Stammerjohn, S. Modeling of the influence of sea ice cycle and Langmuir circulation on the upper ocean mixed layer depth and freshwater distribution at the West Antarctic Peninsula. Journal of Geophysical Research: Oceans, 125(8), (2020): e2020JC016109, doi:10.1029/2020JC016109.
    Description: The Southern Ocean is chronically undersampled due to its remoteness, harsh environment, and sea ice cover. Ocean circulation models yield significant insight into key processes and to some extent obviate the dearth of data; however, they often underestimate surface mixed layer depth (MLD), with consequences for surface water‐column temperature, salinity, and nutrient concentration. In this study, a coupled circulation and sea ice model was implemented for the region adjacent to the West Antarctic Peninsula, a climatically sensitive region which has exhibited decadal trends towards higher ocean temperature, shorter sea ice season, and increasing glacial freshwater input, overlain by strong interannual variability. Hindcast simulations were conducted with different air‐ice drag coefficients and Langmuir circulation parameterizations to determine the impact of these factors on MLD. Including Langmuir circulation deepened the surface mixed layer, with the deepening being more pronounced in the shelf and slope regions. Optimal selection of an air‐ice drag coefficient also increased modeled MLD by similar amounts and had a larger impact in improving the reliability of the simulated MLD interannual variability. This study highlights the importance of sea ice volume and redistribution to correctly reproduce the physics of the underlying ocean, and the potential of appropriately parameterizing Langmuir circulation to help correct for biases towards shallow MLD in the Southern Ocean. The model also reproduces observed freshwater patterns in the West Antarctic Peninsula during late summer and suggests that areas of intense summertime sea ice melt can still show net annual freezing due to high sea ice formation during the winter.
    Description: C. Schultz and S. Doney acknowledge support by the U.S. National Science Foundation (grant PLR‐1440435 to the Palmer Long Term Ecological Research program) and support from the University of Virginia. W. G. Zhang acknowledge support by the U.S. National Science Foundation (grant OPP‐1643901). The MITgcm model is an open source model (mitgcm.org). The version used in this study, with added parameterizations and specific configurations, is on C. Schultz’s github (https://github.com/crisoceano/WAP_MITgcm). A copy of the files with specific configurations for this study, the forcing files needed for the simulations, and a copy of the files used for the KPP package are in three separate records on zenodo.org, under DOIs 10.5281/zenodo.3627365, 10.5281/zenodo.3627564, and 10.5281/zenodo.3627742.
    Keywords: West Antarctic Peninsula ; sea ice ; Langmuir circulation ; mixed layer depth ; glacial runoff
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  • 74
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 50(4), (2020): 1045-1064, doi:10.1175/JPO-D-19-0137.1.
    Description: Three simulations of the circulation in the Gulf of Mexico (the “Gulf”) using different numerical general circulation models are compared with results of recent large-scale observational campaigns conducted throughout the deep (〉1500 m) Gulf. Analyses of these observations have provided new understanding of large-scale mean circulation features and variability throughout the deep Gulf. Important features include cyclonic flow along the continental slope, deep cyclonic circulation in the western Gulf, a counterrotating pair of cells under the Loop Current region, and a cyclonic cell to the south of this pair. These dominant circulation features are represented in each of the ocean model simulations, although with some obvious differences. A striking difference between all the models and the observations is that the simulated deep eddy kinetic energy under the Loop Current region is generally less than one-half of that computed from observations. A multidecadal integration of one of these numerical simulations is used to evaluate the uncertainty of estimates of velocity statistics in the deep Gulf computed from limited-length (4 years) observational or model records. This analysis shows that the main deep circulation features identified from the observational studies appear to be robust and are not substantially impacted by variability on time scales longer than the observational records. Differences in strengths and structures of the circulation features are identified, however, and quantified through standard error analysis of the statistical estimates using the model solutions.
    Description: This work was supported by the Gulf Research Program of the National Academy of Sciences under Awards 2000006422 and 2000009966. The content is solely the responsibility of the authors and does not necessarily represent the official views of the Gulf Research Program or the National Academy of Sciences. The authors acknowledge the GLORYS project for providing the ocean reanalysis data used in the ROMS simulation. GLORYS is jointly conducted by MERCATOR OCEAN, CORIOLIS, and CNRS/INSU. Installation, recovery, data acquisition, and processing of the CANEK group current-meter moorings were possible because of CICESE-PetróleosMexicanos Grant PEP-CICESE 428229851 and the dedicated work of the crew of the B/O Justo Sierra and scientists of the CANEK group. The authors thank Dr. Aljaz Maslo, CICESE, for assistance with analysis of model data. The Bureau of Ocean Energy Management (BOEM), U.S. Dept. of the Interior, provided funding for the Lagrangian Study of the Deep Circulation in the Gulf of Mexico and the Observations and Dynamics of the Loop Current study. HYCOM simulation data are available from the HYCOM data server (https://www.hycom.org/data/goml0pt04/expt-02pt2), MITgcm data are available from the ECCO data server (http://ecco.ucsd.edu/gom_results2.html), and the ROMS simulation data are available from GRIIDC (NA.x837.000:0001).
    Keywords: Ocean circulation ; Abyssal circulation ; Bottom currents/bottom water ; Eddies ; Ocean models
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  • 75
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 125(12),(2020): e2020JC016271, https://doi.org/10.1029/2020JC016271.
    Description: Asian summer monsoon has a planetary‐scale, westward propagating “quasi‐biweekly” mode of variability with a 10–25 day period. Six years of moored observations at 18°N, 89.5°E in the north Bay of Bengal (BoB) reveal distinct quasi‐biweekly variability in sea surface salinity (SSS) during summer and autumn, with peak‐to‐peak amplitude of 3–8 psu. This large‐amplitude SSS variability is not due to variations of surface freshwater flux or river runoff. We show from the moored data, satellite SSS, and reanalyses that surface winds associated with the quasi‐biweekly monsoon mode and embedded weather‐scale systems, drive SSS and coastal sea level variability in 2015 summer monsoon. When winds are calm, geostrophic currents associated with mesoscale ocean eddies transport Ganga‐Brahmaputra‐Meghna river water southward to the mooring, salinity falls, and the ocean mixed layer shallows to 1–10 m. During active (cloudy, windy) spells of quasi‐biweekly monsoon mode, directly wind‐forced surface currents carry river water away to the east and north, leading to increased salinity at the moorings, and rise of sea level by 0.1–0.5 m along the eastern and northern boundary of the bay. During July–August 2015, a shallow pool of low‐salinity river water lies in the northeastern bay. The amplitude of a 20‐day oscillation of sea surface temperature (SST) is two times larger within the fresh pool than in the saltier ocean to the west, although surface heat flux is nearly identical in the two regions. This is direct evidence that spatial‐temporal variations of BoB salinity influences sub‐seasonal SST variations, and possibly SST‐mediated monsoon air‐sea interaction.
    Description: The authors thank the Ministry of Earth Sciences (MoES) institutes NIOT and INCOIS, and the Upper Ocean Processes (UOP) group at WHOI for design, integration, and deployment of moorings in the BoB. The WHOI mooring was deployed from the ORV Sagar Nidhi and recovered from the ORV Sagar Kanya—we thank the officers, crew and science teams on the cruises for their support. Sengupta, Ravichandran and Sukhatme acknowledge MoES and the National Monsoon Mission, Indian Institute of Tropical Meteorology (IITM), Pune, for support; Lucas and Farrar acknowledge the US Office of Naval Research for support of ASIRI through grants N00014‐13‐1‐0489, N0001413‐100453, N0001417‐12880. We thank S. Shivaprasad, Dipanjan Chaudhuri and Jared Buckley for discussion on ocean currents and Ekman flow, and Fabien Durand for discussion on sea level. JSL would like to thank the Divecha Center for Climate Change, IISc., for support. DS acknowledges support from the Department of Science and Technology (DST), New Delhi, under the Indo‐Spanish Programme.
    Description: 2021-05-16
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  • 76
    Publication Date: 2022-10-27
    Description: Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Solid Earth 124(8), (2019): 7525-7537, doi: 10.1029/2019JB018186.
    Description: The proliferation of drilling expeditions focused on characterizing natural gas hydrate as a potential energy resource has spawned widespread interest in gas hydrate reservoir properties and associated porous media phenomena. Between 2017 and 2019, a Special Section of this journal compiled contributed papers elucidating interactions between gas hydrate and sediment based on laboratory, numerical modeling, and field studies. Motivated mostly by field observations in the northern Gulf of Mexico and offshore Japan, several papers focus on the mechanisms for gas hydrate formation and accumulation, particularly with vapor phase gas, not dissolved gas, as the precursor to hydrate. These studies rely on numerical modeling or laboratory experiments using sediment packs or benchtop micromodels. A second focus of the Special Section is the role of fines in inhibiting production of gas from methane hydrate, controlling the distribution of hydrate at a pore scale, and influencing the bulk behavior of seafloor sediments. Other papers fill knowledge gaps related to the physical properties of hydrate‐bearing sediments and advance new approaches in coupled thermal‐mechanical modeling of these sediments during hydrate dissociation. Finally, one study addresses the long‐standing question about the fate of methane hydrate at the molecular level when CO2 is injected into natural reservoirs under hydrate‐forming conditions.
    Description: C. R. was supported by the U.S. Geological Survey's Energy Resources Program and the Coastal/Marine Hazards and Resources Program, as well as by DOE Interagency Agreement DE‐FE0023495. C. R. thanks W. Waite and J. Jang for discussions and suggestions that improved this paper and L. Stern for a helpful review. J. Y. Lee was supported by the Ministry of Trade, Industry, and Energy (MOTIE) through the Project “Gas Hydrate Exploration and Production Study (19‐1143)” under the management of the Gas Hydrate Research and Development Organization (GHDO) of Korea and the Korea Institute of Geoscience and Mineral Resources (KIGAM). Any use of trade, firm, or product name is for descriptive purposes only and does not imply endorsement by the U.S. Government.
    Keywords: Gas hydrate ; Methane ; Reservoir properties ; Multiphase flow
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  • 77
    Publication Date: 2022-10-27
    Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 125(5), (2020): e2019JC015989, doi:10.1029/2019JC015989.
    Description: Relatively minor amounts of methane, a potent greenhouse gas, are currently emitted from the oceans to the atmosphere, but such methane emissions have been hypothesized to increase as oceans warm. Here, we investigate the source, distribution, and fate of methane released from the upper continental slope of the U.S. Mid‐Atlantic Bight, where hundreds of gas seeps have been discovered between the shelf break and ~1,600 m water depth. Using physical, chemical, and isotopic analyses, we identify two main sources of methane in the water column: seafloor gas seeps and in situ aerobic methanogenesis which primarily occurs at 100–200 m depth in the water column. Stable isotopic analyses reveal that water samples collected at all depths were significantly impacted by aerobic methane oxidation, the dominant methane sink in this region, with the average fraction of methane oxidized being 50%. Due to methane oxidation in the deeper water column, below 200 m depth, surface concentrations of methane are influenced more by methane sources found near the surface (0–10 m depth) and in the subsurface (10–200 m depth), rather than seafloor emissions at greater depths.
    Description: This research was supported by DOE Grant (DE‐FE0028980) to J. K. and by DOE‐USGS Interagency Agreement DE‐FE0026195.
    Description: 2020-10-04
    Keywords: Methane ; Ocean ; Isotopes ; Gas seeps ; Mid Atlantic bight ; Oxidation
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  • 78
    Publication Date: 2022-10-27
    Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Biogeosciences 125(1), (2020): e2019JG005222, doi:10.1029/2019JG005222.
    Description: Wetlands play an important role in reducing global warming potential in response to global climate change. Unfortunately, due to the effects of human disturbance and natural erosion, wetlands are facing global extinction. It is essential to implement engineering measures to restore damaged wetlands. However, the carbon sink capacity of restored wetlands is unclear. We examined the seasonal change of greenhouse gas emissions in both restored wetland and natural wetland and then evaluated the carbon sequestration capacity of the restored wetland. We found that (1) the carbon sink capacity of the restored wetland showed clear daily and seasonal change, which was affected by light intensity, air temperature, and vegetation growth, and (2) the annual daytime (8–18 hr) sustained‐flux global warming potential was −11.23 ± 4.34 kg CO2 m−2 y−1, representing a much larger carbon sink than natural wetland (−5.04 ± 3.73 kg CO2 m−2 y−1) from April to December. In addition, the results showed that appropriate tidal flow management may help to reduce CH4 emission in wetland restoration. Thus, we proposed that the restored coastal wetland, via effective engineering measures, reliably acted as a large net carbon sink and has the potential to help mitigate climate change.
    Description: We would like to thank Yangtze Delta Estuarine Wetland Ecosystem Ministry of Education & Shanghai Observation and Research Station for providing sites during our research. This research was supported by the National Key Research and Development Program of China (Grant 2017YFC0506002), the National Natural Science Foundation of China Overseas and Hong Kong‐Macao Scholars Collaborative Research Fund (Grant 31728003), the China Postdoctoral Science Foundation (Grant 2018M640362), the Shanghai University Distinguished Professor (Oriental Scholars) Program (Grant JZ2016006), the Open Fund of Shanghai Key Lab for Urban Ecological Processes and Eco‐Restoration (Grant SHUES2018B06), and the Scientific Projects of Shanghai Municipal Oceanic Bureau (Grant 2018‐03). The complete data set is available at https://data.4tu.nl/repository/uuid:536b2614‐c4ca‐43d2‐84dd‐6180fd859544.
    Keywords: Blue carbon ; Restored wetland ; Sustained‐flux global warming potential (SGWP) ; Greenhouse gas (GHG) ; Carbon sequestration capacity
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  • 79
    Publication Date: 2022-10-27
    Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Earth Surface 125(8),(2020): e2020JF005558, doi:10.1029/2020JF005558.
    Description: Sediment supply is a primary factor in determining marsh response to sea level rise and is typically approximated through high‐resolution measurements of suspended sediment concentrations (SSCs) from adjacent tidal channels. However, understanding sediment transport across the marsh itself remains limited by discontinuous measurements of SSC over individual tidal cycles. Here, we use an array of optical turbidity sensors to build a long‐term, continuous record of SSC across a marsh platform and adjacent tidal channel. We find that channel and marsh concentrations are correlated (i.e., coupled) within tidal cycles but are largely decoupled over longer time scales. We also find that net sediment fluxes decline to near zero within 10 m of the marsh edge. Together, these results suggest that large sections of the marsh platform receive minimal sediment independent of flooding frequency or channel sediment supply. Marsh‐centric, as opposed to channel‐centric, measures of sediment supply may better characterize marsh platform vulnerability.
    Description: This work was funded by NSF Awards 1529245, 1654374, 1426981, 1637630, and 1832221, the NSF Graduate Research Fellowship Program, and the USGS Climate and Land Use Research and Development program. We thank D. Walters, J. Himmelstein, D. Nicks, R. Walker, T. Messerschmidt, and the Plum Island Ecosystems LTER, especially S. Kelsey for laboratory and field assistance. Additionally, we thank C. Friedrichs, G. Guntenspergen, and O. Duran Vinent for contributing ideas that helped develop the work, and the reviewers who helped improve the manuscript. This work is Contribution Number 3928 of the Virginia Institute of Marine Science. In memoriam of David Nicks.
    Description: 2021-01-27
    Keywords: Salt marsh ; Sediment transport ; Turbidity ; Flux convergence ; Decoupling
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  • 80
    Publication Date: 2022-10-27
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Riedel, M., Rohr, K. M. M., Spence, G. D., Kelley, D., Delaney, J., Lapham, L., Pohlman, J. W., Hyndman, R. D., & Willoughby, E. C. Focused fluid flow along the Nootka fault zone and continental slope, explorer-Juan de Fuca Plate Boundary. Geochemistry Geophysics Geosystems, 21(8), (2020): e2020GC009095, doi:10.1029/2020GC009095.
    Description: Geophysical and geochemical data indicate there is abundant fluid expulsion in the Nootka fault zone (NFZ) between the Juan de Fuca and Explorer plates and the Nootka continental slope. Here we combine observations from 〉20 years of investigations to demonstrate the nature of fluid‐flow along the NFZ, which is the seismically most active region off Vancouver Island. Seismicity reaching down to the upper mantle is linked to near‐seafloor manifestation of fluid flow through a network of faults. Along the two main fault traces, seismic reflection data imaged bright spots 100–300 m below seafloor that lie above changes in basement topography. The bright spots are conformable to sediment layering, show opposite‐to‐seafloor reflection polarity, and are associated with frequency reduction and velocity push‐down indicating the presence of gas in the sediments. Two seafloor mounds ~15 km seaward of the Nootka slope are underlain by deep, nonconformable high‐amplitude reflective zones. Measurements in the water column above one mound revealed a plume of warm water, and bottom‐video observations imaged hydrothermal vent system biota. Pore fluids from a core at this mound contain predominately microbial methane (C1) with a high proportion of ethane (C2) yielding C1/C2 ratios 〈500 indicating a possible slight contribution from a deep source. We infer the reflective zones beneath the two mounds are basaltic intrusions that create hydrothermal circulation within the overlying sediments. Across the Nootka continental slope, gas hydrate‐related bottom‐simulating reflectors are widespread and occur at depths indicating heat flow values of 80–90 mW/m2.
    Description: This study represents data from numerous cruises acquired over more than two decades. We would like to thank all the scientific personnel and technical staff involved in data acquisition, processing of samples, and making observations during the ROV dives, as well as the crews and captains of the various research vessels involved. This is contribution #5877 from the University of Maryland Center for Environmental Science. This is NRCan contribution number / Numéro de contribution de RNCan: 20200324.
    Keywords: Fluid flow ; Nootka transform fault ; Gas hydrate ; Intrusion ; Heat flow
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  • 81
    Publication Date: 2022-10-27
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ritschard, E. A., Whitelaw, B., Albertin, C. B., Cooke, I. R., Strugnell, J. M., & Simakov, O. Coupled genomic evolutionary histories as signatures of organismal innovations in cephalopods: co-evolutionary signatures across levels of genome organization may shed light on functional linkage and origin of cephalopod novelties. BioEssays, 41, (2019): 1900073, doi: 10.1002/bies.201900073.
    Description: How genomic innovation translates into organismal organization remains largely unanswered. Possessing the largest invertebrate nervous system, in conjunction with many species‐specific organs, coleoid cephalopods (octopuses, squids, cuttlefishes) provide exciting model systems to investigate how organismal novelties evolve. However, dissecting these processes requires novel approaches that enable deeper interrogation of genome evolution. Here, the existence of specific sets of genomic co‐evolutionary signatures between expanded gene families, genome reorganization, and novel genes is posited. It is reasoned that their co‐evolution has contributed to the complex organization of cephalopod nervous systems and the emergence of ecologically unique organs. In the course of reviewing this field, how the first cephalopod genomic studies have begun to shed light on the molecular underpinnings of morphological novelty is illustrated and their impact on directing future research is described. It is argued that the application and evolutionary profiling of evolutionary signatures from these studies will help identify and dissect the organismal principles of cephalopod innovations. By providing specific examples, the implications of this approach both within and beyond cephalopod biology are discussed.
    Description: E.A.R. and O.S. are supported by the Austrian Science Fund (Grant No. P30686‐B29). E.A.R. is supported by Stazione Zoologica Anton Dohrn (Naples, Italy) PhD Program. The authors wish to thank Graziano Fiorito (SZN, Italy), Hannah Schmidbaur (University of Vienna, Austria), Thomas Hummel (University of Vienna, Austria) for many insightful comments and reading of the draft manuscript. The authors would like to apologize to all colleagues whose work has been omitted due to space constraints.
    Keywords: Cephalopod ; Gene duplication ; Genome rearrangement ; Novel gene ; Organismal innovation
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  • 82
    Publication Date: 2022-10-27
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Arenas Gómez, Claudia M., Sabin, K. Z., & Echeverri, K. Wound healing across the animal kingdom: Crosstalk between the immune system and the extracellular matrix. Developmental Dynamics, (2020): 1-13, doi:10.1002/dvdy.178.
    Description: Tissue regeneration is widespread in the animal kingdom. To date, key roles for different molecular and cellular programs in regeneration have been described, but the ultimate blueprint for this talent remains elusive. In animals capable of tissue regeneration, one of the most crucial stages is wound healing, whose main goal is to close the wound and prevent infection. In this stage, it is necessary to avoid scar formation to facilitate the activation of the immune system and remodeling of the extracellular matrix, key factors in promoting tissue regeneration. In this review, we will discuss the current state of knowledge regarding the role of the immune system and the interplay with the extracellular matrix to trigger a regenerative response.
    Description: The research in the Echeverri lab is supported NIH NCID R01 to Karen Echeverri and start‐up funds from the MBL. Keith Z. Sabin has been supported by an NIH T32 GM113846 grant.
    Keywords: Extracellular matrix ; Immune system ; Regeneration ; Wound healing
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  • 83
    Publication Date: 2022-10-27
    Description: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Biogeosciences 126(1), (2021): e2019JG005621, https://doi.org/10.1029/2019JG005621.
    Description: Ongoing ocean warming can release methane (CH4) currently stored in ocean sediments as free gas and gas hydrates. Once dissolved in ocean waters, this CH4 can be oxidized to carbon dioxide (CO2). While it has been hypothesized that the CO2 produced from aerobic CH4 oxidation could enhance ocean acidification, a previous study conducted in Hudson Canyon shows that CH4 oxidation has a small short‐term influence on ocean pH and dissolved inorganic radiocarbon. Here we expand upon that investigation to assess the impact of widespread CH4 seepage on CO2 chemistry and possible accumulation of this carbon injection along 234 km of the U.S. Mid‐Atlantic Bight. Consistent with the estimates from Hudson Canyon, we demonstrate that a small fraction of ancient CH4‐derived carbon is being assimilated into the dissolved inorganic radiocarbon (mean fraction of 0.5 ± 0.4%). The areas with the highest fractions of ancient carbon coincide with elevated CH4 concentration and active gas seepage. This suggests that aerobic CH4 oxidation has a greater influence on the dissolved inorganic pool in areas where CH4 concentrations are locally elevated, instead of displaying a cumulative effect downcurrent from widespread groupings of CH4 seeps. A first‐order approximation of the input rate of ancient‐derived dissolved inorganic carbon (DIC) into the waters overlying the northern U.S. Mid‐Atlantic Bight further suggests that oxidation of ancient CH4‐derived carbon is not negligible on the global scale and could contribute to deepwater acidification over longer time scales.
    Description: This study was sponsored by U.S. Department of Energy (DE‐FE0028980, awarded to J. D. K; DE‐FE0026195 interagency agreement with C. D. R.). We thank the crew of the R/V Hugh R. Sharp for their support, G. Hatcher, J. Borden, and M. Martini of the USGS for assistance with the LADCP, and Zach Bunnell, Lillian Henderson, and Allison Laubach for additional support at sea.
    Description: 2021-06-23
    Keywords: Radiocarbon ; Methane ; DIC ; Ocean acidification ; Climate change ; U.S Mid-Atlantic Bight
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  • 84
    Publication Date: 2022-10-27
    Description: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 126(10),(2021): e2021JB022050, https://doi.org/10.1029/2021JB022050.
    Description: On-fault earthquake magnitude distributions are calculated for northern Caribbean faults using estimates of fault slip and regional seismicity parameters. Integer programming, a combinatorial optimization method, is used to determine the optimal spatial arrangement of earthquakes sampled from a truncated Gutenberg-Richter distribution that minimizes the global misfit in slip rates on a complex fault system. Slip rates and their uncertainty on major faults are derived from a previously published GPS block model for the region, with fault traces determined from offshore geophysical mapping and previously published onshore studies. The optimal spatial arrangement of the sampled earthquakes is compared with the 500-year history of earthquake observations. Rupture segmentation of the subduction interface along the Hispaniola-Puerto Rico Trench (PRT) fault and seismic coupling on the PRT fault appear to exert the primary control over this spatial arrangement. Introducing a rupture barrier for the Hispaniola-PRT fault northwest of Mona Passage, based on geophysical and seismicity observations, and assigning a low slip rate of 2 mm/yr on the PRT fault are most consistent with historical earthquakes in the region. The addition of low slip-rate secondary faults as well as segmentation of the Hispaniola and Septentrional strike-slip fault improves the consistency with historical seismicity. An important observation from the modeling is that varying the slip rate on the PRT fault and different segmentation scenarios result in significant changes to the optimal magnitude distribution on faults farther away. In general, optimal on-fault magnitude distributions are more complex and inter-dependent than is typically assumed in probabilistic seismic hazard analysis and probabilistic tsunami hazard analysis.
    Description: Funding for this study is from the U.S. Geological Survey Coastal and Marine Hazards and Resources Program.
    Description: 2022-04-11
    Keywords: Northern Caribbean ; Rupture forecast ; Combinatorial optimization ; Integer programming
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  • 85
    Publication Date: 2022-10-27
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Sanders‐DeMott, R., Eagle, M., Kroeger, K., Wang, F., Brooks, T., Suttles, J., Nick, S., Mann, A., & Tang, J. Impoundment increases methane emissions in Phragmites‐invaded coastal wetlands. Global Change Biology, 28(15), (2022): 4539– 4557. https://doi.org/10.1111/gcb.16217.
    Description: Saline tidal wetlands are important sites of carbon sequestration and produce negligible methane (CH4) emissions due to regular inundation with sulfate-rich seawater. Yet, widespread management of coastal hydrology has restricted tidal exchange in vast areas of coastal wetlands. These ecosystems often undergo impoundment and freshening, which in turn cause vegetation shifts like invasion by Phragmites, that affect ecosystem carbon balance. Understanding controls and scaling of carbon exchange in these understudied ecosystems is critical for informing climate consequences of blue carbon restoration and/or management interventions. Here, we (1) examine how carbon fluxes vary across a salinity gradient (4–25 psu) in impounded and natural, tidally unrestricted Phragmites wetlands using static chambers and (2) probe drivers of carbon fluxes within an impounded coastal wetland using eddy covariance at the Herring River in Wellfleet, MA, United States. Freshening across the salinity gradient led to a 50-fold increase in CH4 emissions, but effects on carbon dioxide (CO2) were less pronounced with uptake generally enhanced in the fresher, impounded sites. The impounded wetland experienced little variation in water-table depth or salinity during the growing season and was a strong CO2 sink of −352 g CO2-C m−2 year−1 offset by CH4 emission of 11.4 g CH4-C m−2 year−1. Growing season CH4 flux was driven primarily by temperature. Methane flux exhibited a diurnal cycle with a night-time minimum that was not reflected in opaque chamber measurements. Therefore, we suggest accounting for the diurnal cycle of CH4 in Phragmites, for example by applying a scaling factor developed here of ~0.6 to mid-day chamber measurements. Taken together, these results suggest that although freshened, impounded wetlands can be strong carbon sinks, enhanced CH4 emission with freshening reduces net radiative balance. Restoration of tidal flow to impounded ecosystems could limit CH4 production and enhance their climate regulating benefits.
    Description: This project was supported by USGS-NPS Natural Resources Preservation Program #2021-07, U.S. Geological Survey Coastal & Marine Hazards and Resources Program and the USGS Land Change Science Program's LandCarbon program, and NOAA National Estuarine Research Reserve Science Collaborative NA14NOS4190145. R Sanders-DeMott was supported by a USGS Mendenhall Fellowship and partnership with Restore America's Estuaries.
    Keywords: Blue carbon ; Coastal wetland ; Dike ; Eddy covariance ; Impoundment ; Methane ; Net ecosystem exchange ; Phragmites ; Restoration ; Static chambers
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  • 86
    Publication Date: 2022-10-27
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Fu, X., Waite, W. F., & Ruppel, C. D. Hydrate formation on marine seep bubbles and the implications for water column methane dissolution. Journal of Geophysical Research: Oceans, 126(9), (2021): e2021JC017363, https://doi.org/10.1029/2021JC017363.
    Description: Methane released from seafloor seeps contributes to a number of benthic, water column, and atmospheric processes. At seafloor seeps within the methane hydrate stability zone, crystalline gas hydrate shells can form on methane bubbles while the bubbles are still in contact with the seafloor or as the bubbles begin ascending through the water column. These shells reduce methane dissolution rates, allowing hydrate-coated bubbles to deliver methane to shallower depths in the water column than hydrate-free bubbles. Here, we analyze seafloor videos from six deepwater seep sites associated with a diverse range of bubble-release processes involving hydrate formation. Bubbles that grow rapidly are often hydrate-free when released from the seafloor. As bubble growth slows and seafloor residence time increases, a hydrate coating can form on the bubble's gas-water interface, fully coating most bubbles within ∼10 s of the onset of hydrate formation at the seafloor. This finding agrees with water-column observations that most bubbles become hydrate-coated after their initial ∼150 cm of rise, which takes about 10 s. Whether a bubble is coated or not at the seafloor affects how much methane a bubble contains and how quickly that methane dissolves during the bubble's rise through the water column. A simplified model shows that, after rising 150 cm above the seafloor, a bubble that grew a hydrate shell before releasing from the seafloor will have ∼5% more methane than a bubble of initial equal volume that did not grow a hydrate shell after it traveled to the same height.
    Description: X. Fu acknowledges support from the Miller Fellowship during her time at U.C. Berkeley. W. Waite and C. Ruppel are supported by the United States Geological Survey (USGS) Coastal/Marine Hazards and Resources Program and the Energy Resources Program, with research conducted under USGS-Department of Energy interagency agreements DE-FE0023495 and 89243320SFE000013.
    Keywords: Gas and hydrate systems ; Oceanography: biological and chemical ; Carbon cycling ; Biogeochemical cycles, processes, and modeling
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  • 87
    Publication Date: 2022-10-27
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Loescher, H., Vargas, R., Mirtl, M., Morris, B., Pauw, J., Yu, X., Kutsch, W., Mabee, P., Tang, J., Ruddell, B., Pulsifer, P., Bäck, J., Zacharias, S., Grant, M., Feig, G., Zheng, L., Waldmann, C., & Genazzio, M. Building a global ecosystem research infrastructure to address global grand challenges for macrosystem ecology. Earth’s Future, 10(5), (2022): e2020EF001696, https://doi.org/10.1029/2020ef001696.
    Description: The development of several large-, “continental”-scale ecosystem research infrastructures over recent decades has provided a unique opportunity in the history of ecological science. The Global Ecosystem Research Infrastructure (GERI) is an integrated network of analogous, but independent, site-based ecosystem research infrastructures (ERI) dedicated to better understand the function and change of indicator ecosystems across global biomes. Bringing together these ERIs, harmonizing their respective data and reducing uncertainties enables broader cross-continental ecological research. It will also enhance the research community capabilities to address current and anticipate future global scale ecological challenges. Moreover, increasing the international capabilities of these ERIs goes beyond their original design intent, and is an unexpected added value of these large national investments. Here, we identify specific global grand challenge areas and research trends to advance the ecological frontiers across continents that can be addressed through the federation of these cross-continental-scale ERIs.
    Description: This manuscript is in part the product of several workshops and ongoing GERI development. The first workshop was the Terrestrial Ecosystem Research Network (TERN) sponsored and entitled: “Towards a Global Ecosystem Observatory”, 5–7 March 2017, University of Queensland, Brisbane Australia. Another workshop was sponsored by Chinese Academy of Sciences (CAS) and entitled: “Global Integrated Research Infrastructure component in Next Generation ILTER”, 17–20 April, 2018, South China Botanical Garden, Zhaoqing, Guangdong Province, China. The National Science Foundation (NSF) supported two workshops. The first was entitled: ‘Building a Global Ecological Understanding’ held at the University of Delaware, Newark Delaware, 3–6 June, 2016 (NSF 1347883) and the second entitled: “Global Environmental Research Infrastructure (GERI) Planning Workshop”, held at NEON HQ, Boulder Colorado, 25–27 June 2019 (NSF 1917180). The authors wish to thank the workshop attendees for their thoughtful contributions. NEON is a project sponsored by the NSF and managed under cooperative support agreement (DBI-1029808) to Battelle.
    Keywords: Environmental research infrastructure ; Macrosystem science ; Interoperability ; Societal benefit ; New capabilities ; Federating infrastructure
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  • 88
    Publication Date: 2022-10-27
    Description: This paper is not subject to U.S. copyright. The definitive version was published in Hegermiller, C. A., Warner, J. C., Olabarrieta, M., Sherwood, C. R., & Kalra, T. S. Modeling of barrier breaching during hurricanes Sandy and Matthew. Journal of Geophysical Research: Earth Surface, 127(3), (2022): e2021JF006307, https://doi.org/10.1029/2021JF006307.
    Description: Physical processes driving barrier island change during storms are important to understand to mitigate coastal hazards and to evaluate conceptual models for barrier evolution. Spatial variations in barrier island topography, landcover characteristics, and nearshore and back-barrier hydrodynamics can yield complex morphological change that requires models of increasing resolution and physical complexity to predict. Using the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system, we investigated two barrier island breaches that occurred on Fire Island, NY during Hurricane Sandy (2012) and at Matanzas, FL during Hurricane Matthew (2016). The model employed a recently implemented infragravity (IG) wave driver to represent the important effects of IG waves on nearshore water levels and sediment transport. The model simulated breaching and other changes with good skill at both locations, resolving differences in the processes and evolution. The breach simulated at Fire Island was 250 m west of the observed breach, whereas the breach simulated at Matanzas was within 100 m of the observed breach. Implementation of the vegetation module of COAWST to allow three-dimensional drag over dune vegetation at Fire Island improved model skill by decreasing flows across the back-barrier, as opposed to varying bottom roughness that did not positively alter model response. Analysis of breach processes at Matanzas indicated that both far-field and local hydrodynamics influenced breach creation and evolution, including remotely generated waves and surge, but also surge propagation through back-barrier waterways. This work underscores the importance of resolving the complexity of nearshore and back-barrier systems when predicting barrier island change during extreme events.
    Description: C. A. Hegermiller is grateful to the U.S. Geological Survey (USGS) Mendenhall Research Fellowship Program for support. This project was supported by the USGS Coastal and Marine Geology Program and the Office of Naval Research, Increasing the Fidelity of Morphological Storm Impact Predictions Project. M. Olabarrieta acknowledges support from the NSF project OCE-1554892.
    Description: 2022-07-26
    Keywords: Breach ; Barrier island ; Hurricane
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  • 89
    Publication Date: 2022-10-27
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Zeigler, S. L., Gutierrez, B. T., Lentz, E. E., Plant, N. G., Sturdivant, E. J., & Doran, K. S. Predicted sea-level rise-driven biogeomorphological changes on Fire Island, New York: implications for people and plovers. Earth’s Future, 10(4), (2022): e2021EF002436, https://doi.org/10.1029/2021EF002436.
    Description: Forecasting biogeomorphological conditions for barrier islands is critical for informing sea-level rise (SLR) planning, including management of coastal development and ecosystems. We combined five probabilistic models to predict SLR-driven changes and their implications on Fire Island, New York, by 2050. We predicted barrier island biogeomorphological conditions, dynamic landcover response, piping plover (Charadrius melodus) habitat availability, and probability of storm overwash under three scenarios of shoreline change (SLC) and compared results to observed 2014/2015 conditions. Scenarios assumed increasing rates of mean SLC from 0 to 4.71 m erosion per year. We observed uncertainty in several morphological predictions (e.g., beach width, dune height), suggesting decreasing confidence that Fire Island will evolve in response to SLR as it has in the past. Where most likely conditions could be determined, models predicted that Fire Island would become flatter, narrower, and more overwash-prone with increasing rates of SLC. Beach ecosystems were predicted to respond dynamically to SLR and migrate with the shoreline, while marshes lost the most area of any landcover type compared to 2014/2015 conditions. Such morphological changes may lead to increased flooding or breaching with coastal storms. However—although modest declines in piping plover habitat were observed with SLC—the dynamic response of beaches, flatter topography, and increased likelihood of overwash suggest storms could promote suitable conditions for nesting piping plovers above what our geomorphology models predict. Therefore, Fire Island may offer a conservation opportunity for coastal species that rely on early successional beach environments if natural overwash processes are encouraged.
    Description: Funding for this work was provided by the U.S. Geological Survey's Coastal and Marine Hazards and Resources Program, with supplemental funding through the Disaster Relief Act.
    Keywords: Sea level rise ; Erosion ; Coastal habitats ; Barrier island ; Shorebirds
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  • 90
    Publication Date: 2022-10-27
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Tsakalakis, I., Follows, M. J., Dutkiewicz, S., Follett, C. L., & Vallino, J. J. Diel light cycles affect phytoplankton competition in the global ocean. Global Ecology and Biogeography, 31(9), (2022): 1838-1849, https://doi.org/10.1111/geb.13562.
    Description: Aim Light, essential for photosynthesis, is present in two periodic cycles in nature: seasonal and diel. Although seasonality of light is typically resolved in ocean biogeochemical–ecosystem models because of its significance for seasonal succession and biogeography of phytoplankton, the diel light cycle is generally not resolved. The goal of this study is to demonstrate the impact of diel light cycles on phytoplankton competition and biogeography in the global ocean. Location Global ocean. Major taxa studied Phytoplankton. Methods We use a three-dimensional global ocean model and compare simulations of high temporal resolution with and without diel light cycles. The model simulates 15 phytoplankton types with different cell sizes, encompassing two broad ecological strategies: small cells with high nutrient affinity (gleaners) and larger cells with high maximal growth rate (opportunists). Both are grazed by zooplankton and limited by nitrogen, phosphorus and iron. Results Simulations show that diel cycles of light induce diel cycles in limiting nutrients in the global ocean. Diel nutrient cycles are associated with higher concentrations of limiting nutrients, by 100% at low latitudes (−40° to 40°), a process that increases the relative abundance of opportunists over gleaners. Size classes with the highest maximal growth rates from both gleaner and opportunist groups are favoured by diel light cycles. This mechanism weakens as latitude increases, because the effects of the seasonal cycle dominate over those of the diel cycle. Main conclusions Understanding the mechanisms that govern phytoplankton biogeography is crucial for predicting ocean ecosystem functioning and biogeochemical cycles. We show that the diel light cycle has a significant impact on phytoplankton competition and biogeography, indicating the need for understanding the role of diel processes in shaping macroecological patterns in the global ocean.
    Description: Simons Collaboration on Computational Biogeochemical Modeling of Marine Ecosystems supported M.J.F. and S.D. on CBIOMES grant #549931; C.L.F. on CBIOMES grants #827829 and #553242; and J.J.V. and I.T. on CBIOMES grant #549941. The National Science Foundation supported I.T. and J.J.V. on award #1558710 and J.J.V. on awards #1637630, #1655552 and #1841599.
    Keywords: Biogeography ; Diel light cycle ; Global ocean ; Modelling ; Nutrient cycles ; Phytoplankton ; Resource competition
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  • 91
    Publication Date: 2022-10-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Johnson, H. L., Cessi, P., Marshall, D. P., Schloesser, F., & Spall, M. A. Recent contributions of theory to our understanding of the Atlantic Meridional Overturning Circulation. Journal of Geophysical Research-Oceans, 124(8), (2019): 5376-5399, doi: 10.1029/2019JC015330.
    Description: Revolutionary observational arrays, together with a new generation of ocean and climate models, have provided new and intriguing insights into the Atlantic Meridional Overturning Circulation (AMOC) over the last two decades. Theoretical models have also changed our view of the AMOC, providing a dynamical framework for understanding the new observations and the results of complex models. In this paper we review recent advances in conceptual understanding of the processes maintaining the AMOC. We discuss recent theoretical models that address issues such as the interplay between surface buoyancy and wind forcing, the extent to which the AMOC is adiabatic, the importance of mesoscale eddies, the interaction between the middepth North Atlantic Deep Water cell and the abyssal Antarctic Bottom Water cell, the role of basin geometry and bathymetry, and the importance of a three‐dimensional multiple‐basin perspective. We review new paradigms for deep water formation in the high‐latitude North Atlantic and the impact of diapycnal mixing on vertical motion in the ocean interior. And we discuss advances in our understanding of the AMOC's stability and its scaling with large‐scale meridional density gradients. Along with reviewing theories for the mean AMOC, we consider models of AMOC variability and discuss what we have learned from theory about the detection and meridional propagation of AMOC anomalies. Simple theoretical models remain a vital and powerful tool for articulating our understanding of the AMOC and identifying the processes that are most critical to represent accurately in the next generation of numerical ocean and climate models.
    Description: H. L. J. and D. P. M. are grateful for funding from the U.K. Natural Environment Research Council under the UK‐OSNAP project (NE/K010948/1). P. C. gratefully acknowledges support by the National Science Foundation through OCE‐1634128. M. A. S. was supported by the National Science Foundation Grants OCE‐1558742 and OCE‐1634468. We are also grateful to Eli Tziperman and an anonymous reviewer whose comments helped us to improve the manuscript. The Estimating the Circulation and Climate of the Ocean state estimate (ECCO version 4 release 3) used to produce Figure 2 is available online (https://ecco.jpl.nasa.gov). Please refer to the original papers reviewed here for access to any other data discussed.
    Keywords: Atlantic ; Overturning circulation
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  • 92
    Publication Date: 2022-10-26
    Description: Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 124(8), (2019): 5999-6014, doi: 10.1029/2019JC015034.
    Description: Oceanic fronts are dynamically active regions of the global ocean that support upwelling and downwelling with significant implications for phytoplankton production and export. However (on time scales urn:x-wiley:jgrc:media:jgrc23568:jgrc23568-math-0001 the inertial time scale), the vertical velocity is 103–104 times weaker than the horizontal velocity and is difficult to observe directly. Using intensive field observations in conjunction with a process study ocean model, we examine vertical motion and its effect on phytoplankton fluxes at multiple spatial horizontal scales in an oligotrophic region in the Western Mediterranean Sea. The mesoscale ageostrophic vertical velocity (∼10 m/day) inferred from our observations shapes the large‐scale phytoplankton distribution but does not explain the narrow (1–10 km wide) features of high chlorophyll content extending 40–60 m downward from the deep chlorophyll maximum. Using modeling, we show that downwelling submesoscale features concentrate 80% of the downward vertical flux of phytoplankton within just 15% of the horizontal area. These submesoscale spatial structures serve as conduits between the surface mixed layer and pycnocline and can contribute to exporting carbon from the sunlit surface layers to the ocean interior.
    Description: The AlborEx experiment was conducted in the framework of PERSEUS EU‐funded project (Grant 287600) and was led by the Spanish National Research Council (CSIC) and involved other national and international partners: Balearic Islands Coastal Observing and Forecasting System (SOCIB, Spain); Consiglio Nazionale delle Ricerche (CNR, Italy); Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS, Italy); and Woods Hole Oceanographic Institution (WHOI, ONR Grant N00014‐16‐1‐3130). Glider operations were partially funded by JERICO FP7 project. Part of this work has been carried out as part of the Copernicus Marine Environment Monitoring Service (CMEMS) MedSUB project. CMEMS is implemented by Mercator Ocean in the framework of a delegation agreement with the European Union. S. R. and A. P. acknowledge support from WHOI Subcontract A101339. Data available from authors: Ship CTDs, glider and VM‐ADCP data files are available in the SOCIB data catalog (https://doi.org/10.25704/z5y2-qpye); model data are available at IMEDEA data catalog https://ide.imedea.uib-csic.es/thredds/catalog/data/projects/alborex/catalog.html. We thank all the crew and participants on board R/V SOCIB for their collaboration and Marc Torner and the SOCIB glider Facility for their efficient cooperation. We also thank B. Mourre for numerical data from the Western Mediterranean Operational Model to initialize the Process Study Ocean Model. Figures were created using the cmocean colormaps package (Thyng et al., 2016).
    Keywords: Vertical motion ; Ocean front ; Mesoscale ; Submesoscale ; Transport ; Phytoplankton
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  • 93
    Publication Date: 2022-10-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Little, C. M., Hu, A., Hughes, C. W., McCarthy, G. D., Piecuch, C. G., Ponte, R. M., & Thomas, M. D. The relationship between U.S. East Coast sea level and the Atlantic Meridional Overturning Circulation: a review. Journal of Geophysical Research-Oceans, 124(9), (2019): 6435-6458, doi:10.1029/2019JC015152.
    Description: Scientific and societal interest in the relationship between the Atlantic Meridional Overturning Circulation (AMOC) and U.S. East Coast sea level has intensified over the past decade, largely due to (1) projected, and potentially ongoing, enhancement of sea level rise associated with AMOC weakening and (2) the potential for observations of U.S. East Coast sea level to inform reconstructions of North Atlantic circulation and climate. These implications have inspired a wealth of model‐ and observation‐based analyses. Here, we review this research, finding consistent support in numerical models for an antiphase relationship between AMOC strength and dynamic sea level. However, simulations exhibit substantial along‐coast and intermodel differences in the amplitude of AMOC‐associated dynamic sea level variability. Observational analyses focusing on shorter (generally less than decadal) timescales show robust relationships between some components of the North Atlantic large‐scale circulation and coastal sea level variability, but the causal relationships between different observational metrics, AMOC, and sea level are often unclear. We highlight the importance of existing and future research seeking to understand relationships between AMOC and its component currents, the role of ageostrophic processes near the coast, and the interplay of local and remote forcing. Such research will help reconcile the results of different numerical simulations with each other and with observations, inform the physical origins of covariability, and reveal the sensitivity of scaling relationships to forcing, timescale, and model representation. This information will, in turn, provide a more complete characterization of uncertainty in relevant relationships, leading to more robust reconstructions and projections.
    Description: The authors acknowledge funding support from NSF Grant OCE‐1805029 (C. M. L.) and NASA Contract NNH16CT01C (C. M. L. and R. M. P.), the Regional and Global Model Analysis (RGMA) component of the Earth and Environmental System Modeling Program of the U.S. Department of Energy's Office of Biological & Environmental Research Cooperative Agreement DE‐FC02‐97ER62402 (A. H.), Natural Environment Research Council NE/K012789/1 (C. W. H.), Irish Marine Institute Project A4 PBA/CC/18/01 (G. D. M.), and NSF Awards OCE‐1558966 and OCE‐1834739 (C. G. P.). The National Center for Atmospheric Research is sponsored by National Science Foundation. The authors thank the two reviewers for their comments, and CLIVAR and the U.S. AMOC Science Team for inspiration and patience. All CMIP5 data used in Figures 4-6 are available at http://pcmdi9.llnl.gov/ website; the AMOC strength fields were digitized from Chen et al. (2018, supporting information Figure S3).
    Keywords: Sea level ; AMOC ; United States ; Coastal ; Climate model ; Review
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  • 94
    Publication Date: 2022-10-26
    Description: Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Solid Earth 124 (2019): 10023–10055, doi: 10.1029/2019JB017648.
    Description: We studied long‐term evolution of nontransform discontinuities (NTDs) on the Mid‐Atlantic Ridge from 0‐ to ~20‐ to 25‐Ma crust using plate reconstructions of multibeam bathymetry, long‐range HMR1 sidescan sonar, residual mantle Bouguer gravity anomaly (RMBA), and gravity‐derived crustal thickness. NTDs have propagated north and south with respect to flowlines of relative plate motion and both rapidly and slowly compared to the half spreading rate; at times they have been quasi‐stable. Fast, short‐term (〈2 Myr) propagation is driven by reduced magma supply (increased tectonic extension) in the propagating ridge tip when NTD ridge‐axis offsets are small (≲5 km). Propagation at larger offsets generally is slower and longer term. These NTDs can show classic structures of rift propagation including inner and outer pseudofaults and crustal blocks transferred between ridge flanks by discontinuous jumps of the propagating ridge tip. In all cases crustal transfer occurs within the NTD valley. Aside from ridge‐axis offset, the evolution of NTDs appears to be controlled by three factors: (1) gross volume and distribution of magma supplied to ridge segments as controlled by 3‐D heterogeneities in mantle fertility and/or dynamic upwelling; this controls fundamental ridge segmentation. (2) The lithospheric plumbing system through which magma is delivered to the crust. (3) The consequent focusing of tectonic extension in magma‐poor parts of spreading segments, typically at segment ends, which can drive propagation. We also observe long‐wavelength (5‐10 Myr) RMBA asymmetry between the conjugate ridge flanks, and we attribute this to asymmetric distribution of density anomalies in the upper mantle.
    Description: We thank Tingting Wang for providing plate‐reconstruction codes, Ross Parnell‐Turner for technical support, and Anouk Beniest and an anonymous reviewer for comments that helped to improve the manuscript. We benefited greatly from discussion with the Deep Sea Geodynamics Group of the South China Sea Institute of Oceanology. Figures were drawn using the GMT software of Wessel and Smith (1998). This study was supported by National Natural Science Foundation of China (91628301, 41890813, and U1606401), Chinese Academy of Sciences (Y4SL021001, QYZDY‐SSW‐DQC005, and 133244KYSB20180029), Chinese National 985 Project (1350141509), International Exchange Program for Graduate Students of Tongji University (2016020006), China Scholarship Council (201706260034), and Woods Hole Oceanographic Institution. We thank the crews and science parties of the ARSRP, MAREAST, MODE94, and MODE98 expeditions for their contributions to data acquisition. ARSRP and MAREAST data acquisition was funded by Office of Naval Research grant N00014‐90‐J‐6121 and by U.S. National Science Foundation grant OCE‐9503561, respectively. Access to the original data used in this study is available at https://doi.org/10.26025/z2z7‐kd89.
    Description: 2020-03-11
    Keywords: Mid‐Atlantic Ridge ; Nontransform discontinuity ; Plate reconstruction ; Propagating rift
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  • 95
    Publication Date: 2022-10-26
    Description: Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 124 (2019): 7201-7225, doi: 10.1029/2019JC015520.
    Description: The oceanographic response and atmospheric forcing associated with downwelling along the Alaskan Beaufort Sea shelf/slope is described using mooring data collected from August 2002 to September 2004, along with meteorological time series, satellite data, and reanalysis fields. In total, 55 downwelling events are identified with peak occurrence in July and August. Downwelling is initiated by cyclonic low‐pressure systems displacing the Beaufort High and driving westerly winds over the region. The shelfbreak jet responds by accelerating to the east, followed by a depression of isopycnals along the outer shelf and slope. The storms last 3.25 ± 1.80 days, at which point conditions relax toward their mean state. To determine the effect of sea ice on the oceanographic response, the storms are classified into four ice seasons: open water, partial ice, full ice, and fast ice (immobile). For a given wind strength, the largest response occurs during partial ice cover, while the most subdued response occurs in the fast ice season. Over the two‐year study period, the winds were strongest during the open water season; thus, the shelfbreak jet intensified the most during this period and the cross‐stream Ekman flow was largest. During downwelling, the cold water fluxed off the shelf ventilates the upper halocline of the Canada Basin. The storms approach the Beaufort Sea along three distinct pathways: a northerly route from the high Arctic, a westerly route from northern Siberia, and a southerly route from south of Bering Strait. Differences in the vertical structure of the storms are presented as well.
    Description: The authors thank Paula Fratantoni and Dan Torres for processing the moored profiler and ADCP data, respectively. Data from the SBI mooring array can be found at https://archive.eol.ucar.edu/projects/sbi/all_data.shtml. Funding for the analysis was provided by the following grants: National Science Foundation Grants OCE‐1259618 (N. F. and R. P.), OCE‐1756361 (N. F.), and PLR‐1504333 (N. F. and R. P.); National Oceanic and Atmospheric Administration Grant NA14‐OAR4320158 (R. P. and P. L.); and the Natural Sciences and Engineering Research Council of Canada (K. M.).
    Description: 2020-04-16
    Keywords: Downwelling ; Beaufort Sea ; Shelfbreak ; North Slope ; Arctic cyclone
    Repository Name: Woods Hole Open Access Server
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  • 96
    Publication Date: 2022-10-26
    Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 21(3), (2020): e2019GC008847, doi:10.1029/2019GC008847.
    Description: To learn more about magnetic properties of the lower ocean crust and its contributions to marine magnetic anomalies, gabbro samples were collected from International Ocean Discovery Program Hole U1473A at Atlantis Bank on the Southwest Indian Ridge. Detailed magnetic property work links certain magnetic behaviors and domain states to specific magnetic mineral populations. Measurements on whole rocks and mineral separates included magnetic hysteresis, first‐order reversal curves, low‐temperature remanence measurements, thermomagnetic analysis, and magnetic force microscopy. Characteristics of the thermomagnetic data indicate that the upper ~500 m of the hole has undergone hydrothermal alteration. The thermomagnetic and natural remanent magnetization data are consistent with earlier observations from Hole 735B that show remanence arises from low‐Ti magnetite and that natural remanent magnetizations are up to 25 A m−1 in evolved Fe‐Ti oxide gabbros, but are mostly 〈1 A m−1. Magnetite is present in at least three forms. Primary magnetite is associated with coarse‐grained oxides that are more frequent in the upper part of the hole. This magnetic population is linked to dominantly “pseudo‐single‐domain” behavior that arises from fine‐scale lamellar intergrowths within the large oxides. Deeper in the hole the magnetic signal is more commonly dominated by an interacting single‐domain assemblage most likely found along crystal discontinuities in olivine and/or pyroxene. A third contribution is from noninteracting single‐domain inclusions within plagioclase. Because the concentration of the highly magnetic, oxide‐rich gabbros is greatest toward the surface, the signal from coarse oxides will likely dominate the near‐bottom magnetic anomaly signal at Atlantis Bank.
    Description: This work used samples and data provided by the International Ocean Discovery Program. Funding was provided by the U.S. Science Support Program (J.B.). I.L. has benefited from a Smithsonian Edward and Helen Hintz Secretarial Scholarship. We thank the members of the IODP Expedition 360 Science Party, and the captain and crew of the JOIDES Resolution. Part of this work was done as a Visiting Fellow at the Institute for Rock Magnetism (IRM) at the University of Minnesota. The IRM is made possible through the Instrumentation and Facilities program of the National Science Foundation, Earth Sciences Division, and by funding from the University of Minnesota. We would like to thank IRM staff M. Jackson, P. Solheid, and D. Bilardello for their generous assistance. Many thanks to A. Butula, K. Vernon, and J. Marquardt for their assistance with rock magnetic measurements at UWM and to L. McHenry for assistance with XRD. We also thank two anonymous reviewers for their thoughtful comments that improved the manuscript. Magnetic data associated with this manuscript are available in the Magnetics Information Consortium (MagIC) database at https://www.earthref.org/MagIC/doi/10.1029/2019GC008847. XRD data are available at https://zenodo.org/record/3611642.
    Description: 2020-08-28
    Keywords: Marine magnetic anomalies ; Ocean crust magnetization ; Magnetic mineralogy ; IODP ; Expedition 360 ; JOIDES Resolution
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  • 97
    Publication Date: 2022-10-26
    Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 125(4), (2020): e2020JC016046, doi:10.1029/2020JC016046.
    Description: Momentum input from westerly winds blowing over the Southern Ocean can be modulated by mesoscale surface currents and result in changes in large‐scale ocean circulation. Here, using an eddy‐resolving 1/20 degree ocean model configured near Drake Passage, we evaluate the impact of current‐wind interaction on vertical processes. We find a reduction in momentum input from the wind, reduced eddy kinetic energy, and a modification of Ekman pumping rates. Wind stress curl resulting from current‐wind interaction leads to net upward motion, while the nonlinear Ekman pumping term associated with horizontal gradients of relative vorticity induces net downward motion. The spatially averaged mixed layer depth estimated using a density criteria is shoaled slightly by current‐wind interaction. Current‐wind interaction, on the other hand, enhances the stratification in the thermocline below the mixed layer. Such changes have the potential to alter biogeochemical processes including nutrient supply, biological productivity, and air‐sea carbon dioxide exchange.
    Description: The MITgcm can be obtained online (http://mitgcm.org). The geostrophic current product derived from the sea level anomaly can be downloaded in the Copernicus Marine and Environment Monitoring Service of Ssalto/Duacs gridded “allsat” series and along‐track Sea Level Anomalies, Absolute Dynamic Topographies and Geostrophic velocities over the Global Ocean, Mediterranean Sea, Black Sea, European Seas and Acrtic Ocean areas, in Delayed‐Time and in Near‐Real‐Time. Resources supporting this work were provided by the NASA High‐End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center with the award number SMD‐15‐5752. H. S., J. M., and D. J. M. were supported by the NSF MOBY project (OCE‐1048926 and OCE‐1048897). H. S. acknowledges the support by National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (NRF‐2019R1C1C1003663) and Yonsei University Research Fund of 2018‐22‐0053. D. J. M. also gratefully acknowledges NSF and NASA support, along with the Holger W. Jannasch and Columbus O'Donnell Iselin shared chairs for Excellence in Oceanography. H. Seo acknowledges the support from the ONR (N00014‐17‐1‐2398), NOAA (NA10OAR4310376), and the Andrew W. Mellon Foundation Endowed Fund for Innovative Research at WHOI. We also thank two anonymous referees whose comments significantly improved the presentation of results.
    Description: 2020-09-17
    Keywords: Southern Ocean ; Eddy-wind interaction ; Ekman pumping ; Stratification ; Eddy kinetic energy ; Mixed layer depth
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  • 98
    Publication Date: 2022-10-26
    Description: Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 124 (2019): 7575-7590, doi: 10.1029/2019JC015339.
    Description: Satellite altimetry reveals substantial decadal variability in sea level 𝜁 across the tropical Pacific during 1993–2015. An ocean state estimate that faithfully reproduces the observations is used to elucidate the origin of these low-frequency tropical Pacific 𝜁 variations. Analysis of the hydrostatic equation reveals that recent decadal 𝜁 changes in the tropical Pacific are mainly hermosteric in nature, related to changes in upper-ocean heat content. A forcing experiment performed with the numerical model suggests that anomalous wind stress was an important driver of the relevant heat storage and thermosteric variation. Closed budget diagnostics further clarify that the wind-stress-related thermosteric 𝜁 variation resulted from the joint actions of large-scale ocean advection and local surface heat flux, such that advection controlled the budget over shorter, intraseasonal to interannual time scales, and local surface heat flux became increasingly influential at longer decadal periods. In particular, local surface heat flux was important in contributing to a recent reversal of decadal 𝜁 trends in the tropical Pacific. Contributions from local surface heat flux partly reflect damping latent heat flux tied to wind-stress-driven sea-surface-temperature variations.
    Description: This work was supported by NSF Awards OCE‐1558966 and OCE‐1834739. Support of the ECCO project by the NASA Physical Oceanography, Cryospheric Science, and Modeling, Analysis and Prediction programs is also acknowledged. We thank Ou Wang (NASA JPL) for performing the forcing perturbation experiment. Comments from two anonymous reviewers were helpful. Altimetry observations used in Figures 1 and 2 were downloaded from CSIRO (http://www.cmar.csiro.au/sealevel/sl_data_cmar.html). ECCOv4 output is available on the group website (https://ecco.jpl.nasa.gov/).
    Description: 2020-04-30
    Keywords: Sea‐level change ; Sea‐level variability ; Decadal variability ; Tropical Pacific ; State estimation
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  • 99
    Publication Date: 2022-10-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ramos, R. D., Goodkin, N. F., Siringan, F. P., & Hughen, K. A. Coral records of temperature and salinity in the tropical western Pacific reveal influence of the Pacific Decadal Oscillation since the late nineteenth century. Paleoceanography and Paleoclimatology, 34(8), (2019): 1344-1358, doi: 10.1029/2019PA003684.
    Description: The Pacific Decadal Oscillation (PDO) is a complex aggregate of different atmospheric and oceanographic forcings spanning the extratropical and tropical Pacific. The PDO has widespread climatic and societal impacts, thus understanding the processes contributing to PDO variability is critical. Distinguishing PDO‐related variability is particularly challenging in the tropical Pacific due to the dominance of the El Niño–Southern Oscillation and influence of anthropogenic warming signals. Century‐long western Pacific records of subannual sea surface temperature (SST) and sea surface salinity (SSS), derived from coral Sr/Ca and δ18O profiles, respectively, allow for evaluating different climatic sensitivities and identifying PDO‐related variability in the region. The summer Sr/Ca‐SST record provides evidence of a significant SST increase, likely tied to greenhouse gas emissions. Anthropogenic warming is masked in the winter Sr/Ca‐SST record by interannual to multidecadal scale changes driven by the East‐Asian Winter Monsoon and the PDO. Decadal climate variability during winter is strongly correlated to the PDO, in agreement with other PDO records in the region. The PDO also exerts influence on the SSS difference between the dry and wet season coral δ18O (δ18Oc)‐SSS records through water advection. The PDO and El Niño–Southern Oscillation constructively combine to enhance/reduce advection of saline Kuroshio waters at our site. Overall, we are able to demonstrate that climate records from a tropical reef environment significantly capture PDO variability and related changes over the period of a century. This implies that the tropical western Pacific is a key site in understanding multifrequency climate variability, including its impact on tropical climate at longer timescales.
    Description: The authors would like to thank J. Ossolinski, J. Aggangan, J. Quevedo, R. Lloren, G. Albano, J. Perez, and A. Bolton for their help in acquiring core samples in the field. The detailed comments and suggestions of two anonymous reviewers significantly improved the original manuscript. This research was funded by the National Research Foundation Singapore under its Singapore NRF Fellowship scheme awarded to N. F. Goodkin (National Research Fellow award NRF‐RF2012‐03), as administered by the Earth Observatory of Singapore and the Singapore Ministry of Education under the Research Centers of Excellence initiative and by the Ministry of Education, Singapore through its Academic Research Fund Tier 2 (Project MOE2016‐T2‐1‐016). The coral Sr/Ca and δ18O data generated in this study are available in the supporting information Data Set S1 and are archived at the NOAA NCDC World Data Center for Paleoclimatology (https://www.ncdc.noaa.gov/paleo/study/27271). Other data and resources used in this study were sourced from the following sites: PDO index (http://research.jisao.washington.edu/pdo/PDO.latest); IPO index (https://www.esrl.noaa.gov/psd/data/timeseries/IPOTPI/ipotpi.hadisst2.data); NP index (https://www.esrl.noaa.gov/psd/data/correlation/np.data); PDO and North Pacific SST reconstructions (https://www.ncdc.noaa.gov/data‐access/paleoclimatology‐data); and MTM coherence and phase analysis MATLAB® code (https://www.mathworks.com/matlabcentral/fileexchange/22551‐multi‐taper‐coherence‐method‐with‐bias‐correction).
    Keywords: Coral proxies ; PDO ; ENSO ; EAWM ; Western Pacific
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  • 100
    Publication Date: 2022-10-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ma, Q., Dick, H. J. B., Urann, B., & Zhou, H. Silica-rich vein formation in an evolving stress field, Atlantis Bank Oceanic Core Complex. Geochemistry Geophysics Geosystems, 21(7), (2020): e2019GC008795, doi:10.1029/2019GC008795.
    Description: Drilling 809‐m Hole U1473A in the gabbro batholith at the Atlantis Bank Oceanic Core Complex (OCC) found two felsic vein generations: late magmatic fractionates, rich in deuteric water, hosted by oxide gabbros, and anatectic veins associated with dike intrusion and introduction of seawater‐derived volatiles. Microtextures show a change from compressional to tensional stress during vein formation. Temperatures and oxidation state were obtained from amphibole‐plagioclase and oxide pairs in the adjacent gabbros. Type I veins generally have reverse shear‐sense, with restricted ΔFMQ, high Mt/Ilm ratios, and low‐amphibole Cl/F indicating deuteric fluids. They formed during percolation and fractionation of Fe‐Ti‐rich melts into the primary olivine gabbro. Type II veins are usually hosted by olivine gabbro, occur at dike contacts and the margins of normal‐sense shear zones. They are undeformed or weakly deformed, with highly variable ΔFMQ, low Mt/Ilm ratios, and high‐amphibole Cl/F, indicating seawater‐derived fluids. The detachment fault on which the gabbro massif was emplaced rooted near the base of the dike‐gabbro transition beneath the rift valley. The ingress of seawater volatiles began at 〉800°C and penetrated at least ~590 m into the lower crust during extensional faulting in the rift valley and adjacent rift mountains. The sequence of the felsic vein formation likely reflects asymmetric diapiric flow, with a reversal of the stress regime, and a transition from juvenile to seawater‐derived volatiles. This, in turn, is consistent with fault capture leading to the large asymmetries in spreading rates during OCC formations and heat flow beneath the rift mountains.
    Description: This study was supported by the Chinese National Key Basic Research Program (Grant 2012CB417300). H. Dick and B. Urann were supported by U.S. National Science Foundation (Grant OCE‐MG&G 8371300). Emmanuel Codillo provided numerous useful comments and moral support. We thank N. Chatterjee for assistance in analyzing major element mineral composition in the MIT Electron Microprobe Laboratory. The great contributions of 360 Scientific Party for their initial shipboard description and interpretations of the Hole U1473A cores made this work possible. Special thanks go to C. J. MacLeod, Expedition cochief scientist, and Peter Blum, staff scientist, Stephen Midgley, IODP operations superintendent, and Siem Offshore James Samuel McLelland, offshore installation manager, ship's master Terry Skinner, and the crew and drillers on the JOIDES Resolution.
    Keywords: Felsic veins ; Magma chambers ; Ocean ridge ; Geothermometry ; Flourine‐chlorine ; Dynamics
    Repository Name: Woods Hole Open Access Server
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