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  • American Geophysical Union  (87)
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  • 101
    Publication Date: 2022-10-26
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Wang, O., Lee, T., Piecuch, C., Fukumori, I., Fenty, I., Frederikse, T., Menemenlis, D., Ponte, R., & Zhang, H. Local and remote forcing of interannual sea‐level variability at Nantucket Island. Journal of Geophysical Research: Oceans, 127(6), (2022): e2021JC018275, https://doi.org/10.1029/2021jc018275.
    Description: The relative contributions of local and remote wind stress and air-sea buoyancy forcing to sea-level variations along the East Coast of the United States are not well quantified, hindering the understanding of sea-level predictability there. Here, we use an adjoint sensitivity analysis together with an Estimating the Circulation and Climate of the Ocean (ECCO) ocean state estimate to establish the causality of interannual variations in Nantucket dynamic sea level. Wind forcing explains 67% of the Nantucket interannual sea-level variance, while wind and buoyancy forcing together explain 97% of the variance. Wind stress contribution is near-local, primarily from the New England shelf northeast of Nantucket. We disprove a previous hypothesis about Labrador Sea wind stress being an important driver of Nantucket sea-level variations. Buoyancy forcing, as important as wind stress in some years, includes local contributions as well as remote contributions from the subpolar North Atlantic that influence Nantucket sea level a few years later. Our rigorous adjoint-based analysis corroborates previous correlation-based studies indicating that sea-level variations in the subpolar gyre and along the United States northeast coast can both be influenced by subpolar buoyancy forcing. Forward perturbation experiments further indicate remote buoyancy forcing affects Nantucket sea level mostly through slow advective processes, although coastally trapped waves can cause rapid Nantucket sea level response within a few weeks.
    Description: This research was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). CGP was supported by NASA Sea Level Change Team awards 80NSSC20K1241 and 80NM0018D0004.
    Keywords: Sea level ; Adjoint sensitivity ; Forcing mechanism
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  • 102
    Publication Date: 2022-10-26
    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 Global Biogeochemical Cycles 35(10), (2021): e2021GB007058, https://doi.org/10.1029/2021GB007058.
    Description: Continental shelves are important sources of iron (Fe) in the land-dominated Arctic Ocean. To understand the export of Fe from the Arctic to Baffin Bay (BB) and the North Atlantic, we studied the alteration of the Fe signature in waters transiting the Canadian Arctic Archipelago (CAA). During its transit through the CAA, inflowing Arctic Waters from the Canada Basin become enriched in Fe as result of strong sediment resuspension and enhanced sediment-water interactions (non-reductive dissolution). These high Fe waters are exported to BB, where approximately 10.7 kt of Fe are delivered yearly from Lancaster Sound. Furthermore, if the two remaining main CAA pathways (Jones Sound and Nares Strait) are included, this shelf environment would be a dominant source term of Fe (dFe + pFe: 26–90 kt y−1) to Baffin Bay. The conservative Fe flux estimate (26 kt y−1) is 1.7–38 times greater than atmospheric inputs, and may be crucial in supporting primary production and nitrogen fixation in BB and beyond.
    Description: This work was supported by the Natural Sciences and Engineering Research Council of Canada (Grant NSERC-CCAR), the Northern Scientific Training Program, and by the University of British Columbia through a Four Year Fellowship to B. Rogalla.
    Description: 2022-03-20
    Keywords: Iron distributions ; Sediment resuspension ; Iron export ; Trace metal biogeochemistry ; Canadian Arctic Ocean ; GEOTRACES
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  • 103
    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Durkin, C. A., Buesseler, K. O., Cetinic, I., Estapa, M. L., Kelly, R. P., & Omand, M. A visual tour of carbon export by sinking particles. Global Biogeochemical Cycles, 35(10), (2021): e2021GB006985, https://doi.org/10.1029/2021GB006985.
    Description: To better quantify the ocean's biological carbon pump, we resolved the diversity of sinking particles that transport carbon into the ocean's interior, their contribution to carbon export, and their attenuation with depth. Sinking particles collected in sediment trap gel layers from four distinct ocean ecosystems were imaged, measured, and classified. The size and identity of particles was used to model their contribution to particulate organic carbon (POC) flux. Measured POC fluxes were reasonably predicted by particle images. Nine particle types were identified, and most of the compositional variability was driven by the relative contribution of aggregates, long cylindrical fecal pellets, and salp fecal pellets. While particle composition varied across locations and seasons, the entire range of compositions was measured at a single well-observed location in the subarctic North Pacific over one month, across 500 m of depth. The magnitude of POC flux was not consistently associated with a dominant particle class, but particle classes did influence flux attenuation. Long fecal pellets attenuated most rapidly with depth whereas certain other classes attenuated little or not at all with depth. Small particles (〈100 μm) consistently contributed ∼5% to total POC flux in samples with higher magnitude fluxes. The relative importance of these small particle classes (spherical mini pellets, short oval fecal pellets, and dense detritus) increased in low flux environments (up to 46% of total POC flux). Imaging approaches that resolve large variations in particle composition across ocean basins, depth, and time will help to better parameterize biological carbon pump models.
    Description: This work was supported by an NSF EAGER award to C. A. Durkin (OCE-1703664), M. L. Estapa (OCE-1703422), and M. Omand (OCE-1703336), and also by the NASA EXPORTS program (80NSSC17K0662), a NASA New Investigator award to M. L. Estapa (NNX14AM01G), the Rhode Island Endeavor Program (RIEP), NASA's PACE mission, and the Schmidt Ocean Institute.
    Keywords: Biological carbon pump ; Sediment traps ; Fecal pellets ; Aggregates ; Particles ; Salp
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  • 104
    Publication Date: 2022-10-26
    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: Oceans 126(11), (2021): e2021JC017526, https://doi.org/10.1029/2021JC017526.
    Description: The traditional understanding of the regional circulation in the Northwest Pacific marginal seas is that the Korean Coastal Current flows southward, following the isobaths of 20–50 m. However, an unusual tongue-shaped structure of cold water is observed in satellite SST data in January 2017, indicating a possible offshore spread of cold coastal water into the middle Southern Yellow Sea (SYS). Additional observations, including in situ hydrographic data as well as direct current measurement, also suggest this cross-shelf transport of the Korean Coastal Water in January 2017. Our analysis shows that this flow breaks through the isobaths at ∼37°N, moves southward between 50–75 m, and eventually veers anti-cyclonically at ∼35°N to join the western slope of the SYS. This circulation pattern is further supported by heat budget analysis. Diagnosis of potential vorticity (PV) reveals that the elevated negative PV anomaly imposed by surface wind stress favors this unusual cross-shelf transport. The change of wind pattern, although under a deceasing wind speed condition, plays an important role. This work provides an alternative view of the wintertime circulation pattern and motivates future studies of the variability of the coastal currents over interannual and longer time scales in the SYS.
    Description: his study was supported by the Shandong Provincial Key Research and Development Program (2019JZZY020713, 2019GHY112057), the National Key Research and Development Program (2016YFC1401406, 2016YFA0600900), the National Natural Science Foundation of China (42076010, 42130403), National Fund Committee-Shandong joint fund (U1706215), the Fundamental Research Funds for the Central Universities (2020042010), and Ocean University of China-Woods Hole Oceanographic Institution Cooperative Research Initiative (24887).
    Description: 2022-05-01
    Keywords: Offshore diversion of coastal water ; Korean coastal water (KCW) ; Wind-induced potential vorticity (PV) ; Subtle change in wind direction ; Bathymetric amplification of wind variation ; Sandwiched cold tongue
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  • 105
    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Horner, T. J., Little, S. H., Conway, T. M., Farmer, J. R., Hertzberg, J. E., Janssen, D. J., Lough, A. J. M., McKay, J. L., Tessin, A., Galer, S. J. G., Jaccard, S. L., Lacan, F., Paytan, A., Wuttig, K., & GEOTRACES–PAGES Biological Productivity Working Group Members (2021). Bioactive trace metals and their isotopes as paleoproductivity proxies: an assessment using GEOTRACES-era data. Global Biogeochemical Cycles, 35(11), e2020GB006814. https://doi.org/10.1029/2020GB006814.
    Description: Phytoplankton productivity and export sequester climatically significant quantities of atmospheric carbon dioxide as particulate organic carbon through a suite of processes termed the biological pump. Constraining how the biological pump operated in the past is important for understanding past atmospheric carbon dioxide concentrations and Earth's climate history. However, reconstructing the history of the biological pump requires proxies. Due to their intimate association with biological processes, several bioactive trace metals and their isotopes are potential proxies for past phytoplankton productivity, including iron, zinc, copper, cadmium, molybdenum, barium, nickel, chromium, and silver. Here, we review the oceanic distributions, driving processes, and depositional archives for these nine metals and their isotopes based on GEOTRACES-era datasets. We offer an assessment of the overall maturity of each isotope system to serve as a proxy for diagnosing aspects of past ocean productivity and identify priorities for future research. This assessment reveals that cadmium, barium, nickel, and chromium isotopes offer the most promise as tracers of paleoproductivity, whereas iron, zinc, copper, and molybdenum do not. Too little is known about silver to make a confident determination. Intriguingly, the trace metals that are least sensitive to productivity may be used to track other aspects of ocean chemistry, such as nutrient sources, particle scavenging, organic complexation, and ocean redox state. These complementary sensitivities suggest new opportunities for combining perspectives from multiple proxies that will ultimately enable painting a more complete picture of marine paleoproductivity, biogeochemical cycles, and Earth's climate history.
    Description: T. J. Horner acknowledges support from NSF; S. H. Little from the UK Natural Environment Research Council (NE/P018181/1); T. M. Conway from the University of South Florida; and, J. R. Farmer from the Max Planck Society, the Tuttle Fund of the Department of Geosciences of Princeton University, the Grand Challenges Program of the Princeton Environmental Institute, and the Andlinger Center for Energy and the Environment of Princeton University.
    Keywords: Biological pump ; Marine chemistry ; Biogeochemical cycles ; Micronutrients ; Phytoplankton ; Paleoceanography
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  • 106
    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Brinkmann, I., Ni, S., Schweizer, M., Oldham, V. E., Quintana Krupinski, N. B., Medjoubi, K., Somogyi, A., Whitehouse, M. J., Hansel, C. M., Barras, C., Bernhard, J. M., & Filipsson, H. L. Foraminiferal Mn/Ca as bottom-water hypoxia proxy: an assessment of Nonionella stella in the Santa Barbara Basin, USA. Paleoceanography and Paleoclimatology, 36(11), (2021): e2020PA004167, https://doi.org/10.1029/2020PA004167.
    Description: Hypoxia is of increasing concern in marine areas, calling for a better understanding of mechanisms leading to decreasing dissolved oxygen concentrations ([O2]). Much can be learned about the processes and implications of deoxygenation for marine ecosystems using proxy records from low-oxygen sites, provided proxies, such as the manganese (Mn) to calcium (Ca) ratio in benthic foraminiferal calcite, are available and well calibrated. Here we report a modern geochemical data set from three hypoxic sites within the Santa Barbara Basin (SBB), USA, where we study the response of Mn/Caforam in the benthic foraminifer Nonionella stella to variations in sedimentary redox conditions (Mn, Fe) and bottom-water dissolved [O2]. We combine molecular species identification by small subunit rDNA sequencing with morphological characterization and assign the SBB N. stella used here to a new phylotype (T6). Synchrotron-based scanning X-ray fluorescence (XRF) imaging and Secondary Ion Mass Spectrometry (SIMS) show low Mn incorporation (partition coefficient DMn 〈 0.05) and limited proxy sensitivity of N. stella, at least within the range of dissolved [O2] (2.7–9.6 μmol/l) and Mnpore-water gradients (2.12–21.59 μmol/l). Notably, even though intra- and interspecimen Mn/Ca variability (33% and 58%, respectively) was only partially controlled by the environment, Mn/Caforam significantly correlated with both pore-water Mn and bottom-water [O2]. However, the prevalent suboxic bottom-water conditions and limited dissolved [O2] range complicate the interpretation of trace-elemental trends. Additional work involving other oxygenation proxies and samples from a wider oxygen gradient should be pursued to further develop foraminiferal Mn/Ca as an indicator for hypoxic conditions.
    Description: We acknowledge funding from the Swedish Research Council VR (grant numbers 2017-04190 and 2017-00671), the Crafoord Foundation, and the Royal Physiographic Society in Lund, Sweden. Shiptime provided by US NSF IOS 1557430. We acknowledge SOLEIL for provision of synchrotron radiation facilities and the beamline NANOSCOPIUM (proposal number 20181115). The synchrotron-based experiments were supported by CALIPSOplus under the EU Framework Programme for Research and Innovation HORIZON 2020 (grant agreement 730872). The SIMS analyses were jointly supported by the Swedish Museum of Natural History and Swedish Research Council. This is NordSIMS contribution No. 694. J. M. Bernhard and C. M. Hansel also acknowledge funding from the US National Science Foundation (IOS 1557430).
    Keywords: Benthic foraminifera ; Deoxygenation ; Micro-analytical techniques ; Mn/Ca ; Proxy calibration
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  • 107
    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Hawco, N. J., Barone, B., Church, M. J., Babcock-Adams, L., Repeta, D. J., Wear, E. K., Foreman, R. K., Bjorkman, K. M., Bent, S., Van Mooy, B. A. S., Sheyn, U., DeLong, E. F., Acker, M., Kelly, R. L., Nelson, A., Ranieri, J., Clemente, T. M., Karl, D. M., & John, S. G. Iron depletion in the deep chlorophyll maximum: mesoscale eddies as natural iron fertilization experiments. Global Biogeochemical Cycles, 35(12), (2021): e2021GB007112, https://doi.org/10.1029/2021GB007112.
    Description: In stratified oligotrophic waters, phytoplankton communities forming the deep chlorophyll maximum (DCM) are isolated from atmospheric iron sources above and remineralized iron sources below. Reduced supply leads to a minimum in dissolved iron (dFe) near 100 m, but it is unclear if iron limits growth at the DCM. Here, we propose that natural iron addition events occur regularly with the passage of mesoscale eddies, which alter the supply of dFe and other nutrients relative to the availability of light, and can be used to test for iron limitation at the DCM. This framework is applied to two eddies sampled in the North Pacific Subtropical Gyre. Observations in an anticyclonic eddy center indicated downwelling of iron-rich surface waters, leading to increased dFe at the DCM but no increase in productivity. In contrast, uplift of isopycnals within a cyclonic eddy center increased supply of both nitrate and dFe to the DCM, and led to dominance of picoeukaryotic phytoplankton. Iron addition experiments did not increase productivity in either eddy, but significant enhancement of leucine incorporation in the light was observed in the cyclonic eddy, a potential indicator of iron stress among Prochlorococcus. Rapid cycling of siderophores and low dFe:nitrate uptake ratios also indicate that a portion of the microbial community was stressed by low iron. However, near-complete nitrate drawdown in this eddy, which represents an extreme case in nutrient supply compared to nearby Hawaii Ocean Time-series observations, suggests that recycling of dFe in oligotrophic ecosystems is sufficient to avoid iron limitation in the DCM under typical conditions.
    Description: The expedition and analyses were supported by the Simons Foundation SCOPE Grant 329108 to S. G. John, M. J. Church, D. J. Repeta, B. Van Mooy, E. F. DeLong, and D. M. Karl. N. J. Hawco was supported by a Simons Foundation Marine Microbial Ecology and Evolution postdoctoral fellowship (602538) and Simons Foundation grant 823167.
    Keywords: Chlorophyll ; Photosynthesis ; Iron limitation ; Oligotrophic ; Prochlorococcus ; Eddies
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  • 108
    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Hudak, M. R., Bindeman, I. N., Loewen, M. W., & Giachetti, T. Syn-eruptive hydration of volcanic ash records pyroclast-water interaction in explosive eruptions. Geophysical Research Letters, 48(23), (2021): e2021GL094141, https://doi.org/10.1029/2021GL094141.
    Description: Magma-water interaction can dramatically influence the explosivity of volcanic eruptions. However, syn- and post-eruptive diffusion of external (non-magmatic) water into volcanic glass remains poorly constrained and may bias interpretation of water in juvenile products. Hydrogen isotopes in ash from the 2009 eruption of Redoubt Volcano, Alaska, record syn-eruptive hydration by vaporized glacial meltwater. Both ash aggregation and hydration occurred in the wettest regions of the plume, which resulted in the removal and deposition of the most hydrated ash in proximal areas 〈50 km from the vent. Diffusion models show that the high temperatures of pyroclast-water interactions (〉400°C) are more important than the cooling rate in facilitating hydration. These observations suggest that syn-eruptive glass hydration occurred where meltwater was entrained at high temperature, in the plume margins near the vent. Ash in the drier plume interior remained insulated from entrained meltwater until it cooled sufficiently to avoid significant hydration.
    Description: This work was supported by a Geological Society of America Bruce L. "Biff" Reed Scholarship Award and NSF Grant EAR 1822977.
    Description: 2022-05-15
    Keywords: Volcanic plumes ; Volcanic ash ; Glass hydration ; Phreatomagmatic ; Hydrogen isotopes ; H2O diffusion
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  • 109
    Publication Date: 2022-10-26
    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: Oceans 126(12), (2021): e2021JC017860, https://doi.org/10.1029/2021JC017860.
    Description: An appropriate proxy could help to better understand dissolved oxygen variations in the past, helping to predict potential outcomes of future environmental changes. In the Changjiang Estuary (China), the foraminifer Cribrononion subincertum (C. subincertum) shows a distinct population maximum in the topmost sediment, an indication of an epifaunal species. Therefore, the geochemical composition of C. subincertum tests could record changes in the region’s bottom water chemistry. Our results showed that Mn/Ca ratios in tests of living (Rose-Bengal stained) C. subincertum analyzed by LA-ICP-MS were responsive to variations of bottom water dissolved oxygen concentrations, with average foraminiferal Mn/Ca ratios three times higher during low-oxygen period than in winter. In the uppermost centimeters of sediment, wider ranges of foraminiferal Mn/Ca occurred in summer compared to winter ranges. Our results imply that this epifaunal benthic foraminiferal species could serve as a useful benthic monitor with the Mn/Ca ratios representing a reliable proxy of hypoxia in the past.
    Description: This study was financially supported by the Natural Science Foundation of China (NSFC Grants 41876075, 42130410, and 41620104001), and Fundamental Research Funds for the Central Universities (201841007, 201962003, and 201961012). JMB acknowledges the Investment in Science Fund at WHOI, which supported her participation in this project.
    Description: 2022-06-17
    Keywords: Epifaunal benthic foraminifera ; Mn/Ca ratio ; Coastal hypoxia ; Proxy ; LA-ICP-MS
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  • 110
    Publication Date: 2022-10-26
    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 Global Biogeochemical Cycles 36(1), (2022): e2021GB007113, https://doi.org/10.1029/2021GB007113.
    Description: Stordalen Mire is a peatland in the discontinuous permafrost zone in arctic Sweden that exhibits a habitat gradient from permafrost palsa, to Sphagnum bog underlain by permafrost, to Eriophorum-dominated fully thawed fen. We used three independent approaches to evaluate the annual, multi-decadal, and millennial apparent carbon accumulation rates (aCAR) across this gradient: seven years of direct semi-continuous measurement of CO2 and CH4 exchange, and 21 core profiles for 210Pb and 14C peat dating. Year-round chamber measurements indicated net carbon balance of −13 ± 8, −49 ± 15, and −91 ± 43 g C m−2 y−1 for the years 2012–2018 in palsa, bog, and fen, respectively. Methane emission offset 2%, 7%, and 17% of the CO2 uptake rate across this gradient. Recent aCAR indicates higher C accumulation rates in surface peats in the palsa and bog compared to current CO2 fluxes, but these assessments are more similar in the fen. aCAR increased from low millennial-scale levels (17–29 g C m−2 y−1) to moderate aCAR of the past century (72–81 g C m−2 y−1) to higher recent aCAR of 90–147 g C m−2 y−1. Recent permafrost collapse, greater inundation and vegetation response has made the landscape a stronger CO2 sink, but this CO2 sink is increasingly offset by rising CH4 emissions, dominated by modern carbon as determined by 14C. The higher CH4 emissions result in higher net CO2-equivalent emissions, indicating that radiative forcing of this mire and similar permafrost ecosystems will exert a warming influence on future climate.
    Description: We would like to acknowledge the following funding in support of this project: Swedish Research Council (Vetenskapsrådet, VR) grants (NT 2007-4547 and NT 2013-5562 to P. Crill), U.S. Department of Energy grants (DE-SC0004632 and DE-SC0010580 to V. Rich and S. Saleska), and U.S. National Science Foundation MacroSystems Biology grant (NSF EF #1241037, PI Varner). This work was supported by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research under the Genomic Science program. We also acknowledge funding from the National Science Foundation for the EMERGE Biology Integration Institute, NSF Award #2022070.
    Description: 2022-07-03
    Keywords: Peat ; Carbon cycling ; Permafrost ; Carbon-14 ; Lead-210 ; Climate change
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  • 111
    Publication Date: 2022-10-26
    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 Journal of Geophysical Research: Oceans 127(1), (2022): e2021JC017424, https://doi.org/10.1029/2021JC017424.
    Description: By compiling boreal summer (June to October) CO2 measurements from 1989 to 2019 on the Bering and eastern Chukchi Sea shelves, we find that the study areas act as a CO2 sink except when impacted by river runoff and wind-driven upwelling. The CO2 system in this area is seasonally dominated by the biological pump especially in the northern Bering Sea and near Hanna Shoal, while wind-driven upwelling of CO2-rich bottom water can cause episodic outgassing. Seasonal surface ΔfCO2 (oceanic fCO2 – air fCO2) is dominantly driven by temperature only during periods of weak CO2 outgassing in shallow nearshore areas. However, after comparing the mean summer ΔfCO2 during the periods of 1989–2013 and 2014–2019, we suggest that temperature does drive long-term, multi-decadal patterns in ΔfCO2. In the northern Chukchi Sea, rapid warming concurrent with reduced seasonal sea-ice persistence caused the regional summer CO2 sink to decrease. By contrast, increasing primary productivity caused the regional summer CO2 sink on the Bering Sea shelf to increase over time. While additional time series are needed to confirm the seasonal and annual trajectory of CO2 changes and ocean acidification in these dynamic and spatially complex ecosystems, this study provides a meaningful mechanistic analysis of recent changes in inorganic carbonate chemistry. As high-resolution time series of inorganic carbonate parameters lengthen and short-term variations are better constrained in the coming decades, we will have stronger confidence in assessing the mechanisms contributing to long-term changes in the source/sink status of regional sub-Arctic seas.
    Description: We gratefully acknowledge the support of the funding agencies that supported this analysis, including the New Sustained Observations for Arctic Research project and the DBO-NCIS project (NA14OAR4320158, NA19OAR4320074) from the NOAA Arctic Research Program.
    Description: 2022-06-17
    Keywords: Pacific Arctic region ; Sea-air CO2 flux ; Ocean acidification ; Climate change ; Sea-ice loss ; Surface ocean CO2 Atlas
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  • 112
    Publication Date: 2022-10-26
    Description: © The Author(s), [year]. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Barreyre, T., Parnell‐Turner, R., Wu, J., & Fornari, D. Tracking crustal permeability and hydrothermal response during seafloor eruptions at the East Pacific Rise, 9°50’N. Geophysical Research Letters, 49(3), (2022): e2021GL095459, https://doi.org/10.1029/2021gl095459.
    Description: Permeability controls energy and matter fluxes in deep-sea hydrothermal systems fueling a 'deep biosphere' of microorganisms. Here, we indirectly measure changes in sub-seafloor crustal permeability, based on the tidal response of high-temperature hydrothermal vents at the East Pacific Rise 9°50’N preceding the last phase of volcanic eruptions during 2005–2006. Ten months before the last phase of the eruptions, permeability decreased, first rapidly, and then steadily as the stress built up, until hydrothermal flow stopped altogether ∼2 weeks prior to the January 2006 eruption phase. This trend was interrupted by abrupt permeability increases, attributable to dike injection during last phase of the eruptions, which released crustal stress, allowing hydrothermal flow to resume. These observations and models suggest that abrupt changes in crustal permeability caused by magmatic intrusion and volcanic eruption can control first-order hydrothermal circulation processes. This methodology has the potential to aid eruption forecasting along the global mid-ocean ridge network.
    Description: This research is funded by National Science Foundation (NSF) grants to D. J. Fornari and T. Barreyre (OCE-1949485), and to R. Parnell-Turner (OCE-1948936). T. Barreyre was supported by the University of Bergen, Norway.
    Keywords: Hydrothermalism ; Volcanic eruption ; Permeability ; Ocean tides ; Vent temperature
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  • 113
    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Fan, S., Cross, A. J., Prior, D. J., Goldsby, D. L., Hager, T. F., Negrini, M., & Qi, C. Crystallographic preferred orientation (CPO) development governs strain weakening in ice: insights from high-temperature deformation experiments. Journal of Geophysical Research: Solid Earth, 126(12), (2021): e2021JB023173, https://doi.org/10.1029/2021JB023173.
    Description: Strain weakening leads to the formation of high-strain shear zones and strongly influences terrestrial ice discharge. In glacial flow models, strain weakening is assumed to arise from the alignment of weak basal planes—the development of a crystallographic preferred orientation, CPO—during flow. However, in experiments, ice strain weakening also coincides with grain size reduction, which has been invoked as a weakening mechanism in other minerals. To interrogate the relative contributions of CPO development and grain size reduction toward ice strain weakening, we deformed initially isotropic polycrystalline ice samples to progressively higher strains between −4 and −30°C. Microstructural measurements were subsequently combined with flow laws to separately model the mechanical response expected to arise from CPO development and grain size reduction. Magnitudes of strain weakening predicted by the constitutive flow laws were then compared with the experimental measurements. Flow laws that only consider grain size do not predict weakening with strain despite grain size reduction. In contrast, flow laws solely considering CPO effects can reproduce the measured strain weakening. Thus, it is reasonable to assume that strain weakening in ice is dominated by CPO development, at least under high temperature (Th ≥ 0.9) and high stress (〉1 MPa), like those in our experiments. We speculate that at high homologous temperatures (Th ≥ 0.9), CPO development will also govern the strain weakening behavior of other viscously anisotropic minerals, like olivine and quartz. Overall, we emphasize that geodynamic and glaciological models should incorporate CPOs to account for strain weakening, especially at high homologous temperatures.
    Description: This work was supported by a NASA fund (grant no. NNX15AM69G) to David L. Goldsby and two Marsden Funds of the Royal Society of New Zealand (grant nos. UOO1116, UOO052) to David J. Prior. Sheng Fan was supported by the University of Otago doctoral scholarship, the Antarctica New Zealand doctoral scholarship, a research grant from New Zealand Ministry of Business, Innovation and Employment through the Antarctic Science Platform (ANTA1801) (grant no. ASP-023-03), and a New Zealand Antarctic Research Institute (NZARI) Early Career Researcher Seed Grant (grant no. NZARI 2020-1-5).
    Keywords: High-temperature deformation ; Ice ; Strain weakening ; Grain size ; Crystallographic preferred orientation (CPO) ; Electron backscatter diffraction (EBSD)
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 114
    Publication Date: 2022-11-15
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Shero, M. R., Kirkham, A. L., Costa, D. P., & Burns, J. M. Iron mobilization during lactation reduces oxygen stores in a diving mammal. Nature Communications, 13(1), (2022): 4322, https://doi.org/10.1038/s41467-022-31863-7.
    Description: The profound impacts that maternal provisioning of finite energy resources has on offspring survival have been extensively studied across mammals. This study shows that in addition to calories, high hemoprotein concentrations in diving mammals necessitates exceptional female-to-pup iron transfer. Numerous indices of iron mobilization (ferritin, serum iron, total-iron-binding-capacity, transferrin saturation) were significantly elevated during lactation in adult female Weddell seals (Leptonychotes weddellii), but not in skip-breeders. Iron was mobilized from endogenous stores for incorporation into the Weddell seal’s milk at concentrations up to 100× higher than terrestrial mammals. Such high rates of iron offload to offspring drew from the female’s own heme stores and led to compromised physiologic dive capacities (hemoglobin, myoglobin, and total body oxygen stores) after weaning their pups, which was further reflected in shorter dive durations. We demonstrate that lactational iron transfer shapes physiologic dive thresholds, identifying a cost of reproduction to a marine mammal.
    Description: This research was conducted with support from NSF ANT-0838892 to DPC; ANT-0838937 and ANT-1246463 to JMB (which also supported ALK and MRS); and The Investment in Science Fund at WHOI to MRS.
    Keywords: Animal physiology ; Ecophysiology ; Homeostasis
    Repository Name: Woods Hole Open Access Server
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  • 115
    Publication Date: 2022-10-21
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Slater, D., Carroll, D., Oliver, H., Hopwood, M., Straneo, F., Wood, M., Willis, J., & Morlighem, M. Characteristic depths, fluxes and timescales for Greenland’s tidewater glacier fjords from subglacial discharge‐driven upwelling during summer. Geophysical Research Letters, 49(10),(2022): e2021GL097081, https://doi.org/10.1029/2021gl097081.
    Description: Greenland's glacial fjords are a key bottleneck in the earth system, regulating exchange of heat, freshwater and nutrients between the ice sheet and ocean and hosting societally important fisheries. We combine recent bathymetric, atmospheric, and oceanographic data with a buoyant plume model to show that summer subglacial discharge from 136 tidewater glaciers, amounting to 0.02 Sv of freshwater, drives 0.6–1.6 Sv of upwelling. Bathymetric analysis suggests that this is sufficient to renew most major fjords within a single summer, and that these fjords provide a path to the continental shelf that is deeper than 200 m for two-thirds of the glaciers. Our study provides a first pan-Greenland inventory of tidewater glacier fjords and quantifies regional and ice sheet-wide upwelling fluxes. This analysis provides important context for site-specific studies and is a step toward implementing fjord-scale heat, freshwater and nutrient fluxes in large-scale ice sheet and climate models.
    Description: DAS acknowledges support from NERC Independent Research Fellowship NE/T011920/1. DAS and FS acknowledge support from NSF award 2020547. HO acknowledges support from a WHOI Postdoctoral Scholar award. MW and JKW performed this work at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
    Keywords: Greenland Ice Sheet ; Fjord ; Subglacial discharge ; Plume ; Tidewater glacier ; Freshwater
    Repository Name: Woods Hole Open Access Server
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  • 116
    Publication Date: 2022-09-16
    Description: Marine protists abound, but are challenging to study, and their interactions with other microbes in nature remain largely unknown. We captured wild predatory protists (choanoflagellates) and discovered a divergent, obligately co-associated bacterial group that lives by extracting resources from these predators.
    Type: Article , NonPeerReviewed
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  • 117
    Publication Date: 2022-09-22
    Description: This dataset contains PISM simulation results of the Antarctic Ice Sheet based on code release v1.0-paleo-ensemble (https://doi.org/10.5281/zenodo.3574033). PISM is the open-source Parallel Ice Sheet Model developed mainly at UAF, USA and PIK, Germany. See documentation in https://www.pism.io. These are additional netCDF data from the same ensemble simulations already stored in doi:10.1594/PANGAEA.909728. 1) 1000-year snapshots since 125000 years before present, of ice thickness, bed topography, change in bed topography, floating/grounded mask, surface elevation, basal melt rate and vertically averaged velocity magnitude (SIA+SSA) (16GB) 2) 5000-year snapshots since 125000 years before present, SSA velocity components in x and y direction (8GB)
    Type: info:eu-repo/semantics/workingPaper
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  • 118
    Publication Date: 2022-11-14
    Description: The Indo-Pacific Warm Pool (IPWP) exerts a dominant role in global climate by releasing huge amounts of water vapour and latent heat to the atmosphere and modulating upper ocean heat content (OHC), which has been implicated in modern climate change1. The long-term variations of IPWP OHC and their effect on monsoonal hydroclimate are, however, not fully explored. Here, by combining geochemical proxies and transient climate simulations, we show that changes of IPWP upper (0–200 m) OHC over the past 360,000 years exhibit dominant precession and weaker obliquity cycles and follow changes in meridional insolation gradients, and that only 30%–40% of the deglacial increases are related to changes in ice volume. On the precessional band, higher upper OHC correlates with oxygen isotope enrichments in IPWP surface water and concomitant depletion in East Asian precipitation as recorded in Chinese speleothems. Using an isotope-enabled air–sea coupled model, we suggest that on precessional timescales, variations in IPWP upper OHC, more than surface temperature, act to amplify the ocean–continent hydrological cycle via the convergence of moisture and latent heat. From an energetic viewpoint, the coupling of upper OHC and monsoon variations, both coordinated by insolation changes on orbital timescales, is critical for regulating the global hydroclimate.
    Type: Article , PeerReviewed
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