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  • Elsevier  (292,457)
  • Copernicus  (36,241)
  • Institute of Electrical and Electronics Engineers (IEEE)  (26,651)
  • 2015-2019  (355,349)
  • 1990-1994  (2)
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  • 1
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    The combined inversion of seismological and GOCE gravity data: New insights into the current state of the Pacific lithosphere and upper mantle (2017)
    Elsevier
    Details
    Publication Date: 2021-02-26
    Description: In this study we combine seismological and GOCE satellite gravity information by using a Bayesian-like technique, with the aim of inferring the density structure of the Pacific (90°N 90°S) (121°E 60°W) lithosphere and upper mantle. We recover a 1° × 1° 3-D density model, down to 300 km depth, which explains gravity observations with a variance reduction of 67.41%. The model, with an associated a posteriori standard deviation, provides a significant contribution to understanding the evolution of the Pacific lithosphere and answers to some debated geodynamic questions. Our methodology enables us to combine the recovery of density parameters with the optimum density-vSV scalings. The latter account for both seismological and gravity observations in order to identify the regions characterized by chemically-induced density heterogeneities which add to the thermally-induced anoma- lies. Chemically-modified structures are found west of the East Pacific Rise (EPR) and are of relevant amplitude both below the north-western side of the Pacific Plate, at the base of the lithosphere, and up to 100 km depth beneath the Hawaiian and Super Swell regions, thus explaining the anomalous shallow regions without invoking the thermal buoyancy as the sole justification. Coherently with the chemically modified structures, our results a) support a lighter and more buoyant lithosphere than that predicted by the cooling models and b) are in favor of the hypothesized crustal underplating beneath the Hawaiian chain and be- neath the volcanic units in the southern branch of the Super Swell region. The comparison between calculated mantle gravity residuals and residual topography a) suggests a lateral viscosity growth associated with the increasing thickness and density of the Plate and b) correlates well with sub-lithospheric mantle flow from the EPR towards west, up to the Kermadec and Tonga Trench in the south and the Kuril-Kamchatka Trench in the north.
    Description: Published
    Description: 101-115
    Description: 7T. Struttura della Terra e geodinamica
    Description: JCR Journal
    Keywords: Pacific lithosphere ; GOCE ; Satellite gravity ; Seismological observations ; Residual Topography ; 04.07. Tectonophysics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 2
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    Volatile contents of mafic-to-intermediate magmas at San Cristóbal volcano in Nicaragua (2017)
    Elsevier
    Details
    Publication Date: 2021-02-10
    Description: San Cristóbal volcano in northwest Nicaragua is one of the most active basaltic–andesitic stratovolcanoes of the Central American Volcanic Arc (CAVA). Here we provide novel constraints on the volcano's magmatic plumbing system, by presenting the first direct measurements of major volatile contents in mafic-to-intermediate glass inclusions from Holocene and historic-present volcanic activity. Olivine-hosted (forsterite [Fo] b80; Fob80) glass inclusions from Holocene tephra layers contain moderate amounts of H2O (0.1–3.3 wt%) and S and Cl up to 2500 μg/g, and define the mafic (basaltic) endmember component. Historic-present scoriae and tephra layers exhibit more-evolved olivines (Fo69–72) that contain distinctly lower volatile contents (0.1–2.2 wt% H2O, 760–1675 μg/g S, and 1021–1970 μg/g Cl), and represent a more-evolved basaltic–andesitic magma. All glass inclusions are relatively poor in CO2, with contents reaching 527 μg/g (as measured by nanoscale secondary ion mass spectrometry), suggesting pre- to postentrapment CO2 loss to a magmatic vapor. We use results of Raman spectroscopy obtained in a population of small (b50 μm) inclusions with CO2-bearing shrinkage bubbles (3–12 μm) to correct for postentrapment CO2 loss to bubbles, and to estimate the original minimumCO2 content in San Cristóbal parental melts at ~1889 μg/g, which is consistent with the less-CO2-degassed melt inclusions (MI) (N1500 μg/g) found in Nicaragua at Cerro Negro, Nejapa, and Granada. Models of H2O and CO2 solubilities constrain the degassing pathway of magmas up to 425 MPa (~16 km depth), which includes a deep CO2 degassing step (only partially preserved in the MI record), followed by coupled degassing of H2O and S plus crystal fractionation at magma volatile saturation pressures from ∼195 to b10 MPa. The variation in volatile contents from San Cristóbal MI is interpreted to reflect (1) Holocene eruptive cycles characterized by the rapid emplacement of basaltic magma batches, saturated in volatiles, at depths of 3.8–7.4 km, and (2) the ascent of more-differentiated and cogenetic volatile-poor basaltic andesites during historic-present eruptions, having longer residence times in the shallowest (b3.4 km) and hence coolest regions of the magmatic plumbing system. We also report the first measurements of the compositions of noble-gas isotopes (He, Ne, and Ar) in fluid inclusions in olivine and pyroxene crystals. While the measured 40Ar/36Ar ratios (300–304) and 4He/20Ne ratios (9–373) indicate some degree of air contamination, the 3He/4He ratios (7.01–7.20 Ra) support a common mantle source for Holocene basalts and historic-present basaltic andesites. The magmatic source is interpreted as generated by a primitive MORB-like mantle, that is influenced to variable extents by distinct slab fluid components for basalts (Ba/La ~ 76 and U/Th ~ 0.8) and basaltic andesites (Ba/La ~ 86 and U/Th ~ 1.0) in addition to effects of magma differentiation. These values for the geochemical markers are particularly high, and their correlation with strong plume CO2/S ratios from San Cristóbal is highly consistent with volatile recycling at the CAVA subduction zone, where sediment involvement in mantle fluids influences the typical relatively C-rich signature of volcanic gases in Nicaragua.
    Description: Published
    Description: 131-148
    Description: 1V. Storia eruttiva
    Description: JCR Journal
    Keywords: San Cristóbal, Volatiles, Melt inclusions, NanoSIMS, Multi-GAS, Noble gases ; Volcanology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 3
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    Uncovering deformation processes from surface displacements (2016)
    Elsevier
    Details
    Publication Date: 2021-05-12
    Description: Today, satellite remote sensing has reached a key role in Earth Sciences. In particular, Synthetic ApertureRadar (SAR) sensors and SAR Interferometry (InSAR) techniques are widely used for the study of dynamicprocesses occurring inside our living planet. Over the past 3 decades, InSAR has been applied for mappingtopography and deformation at the Earth’s surface. These maps are widely used in tectonics, seismology,geomorphology, and volcanology, in order to investigate the kinematics and dynamics of crustal faulting,the causes of postseismic and interseismic displacements, the dynamics of gravity driven slope failures,and the deformation associated with subsurface movement of water, hydrocarbons or magmatic fluids.
    Description: Published
    Description: 58-82
    Description: 1T. Geodinamica e interno della Terra
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: 3V. Dinamiche e scenari eruttivi
    Description: JCR Journal
    Description: reserved
    Keywords: SAR ; InSAR ; Earth observation ; Surface displacements ; Satellite missions ; Advanced InSAR ; Earthquake studies ; Volcanic studies ; Tectonic process ; Coseismic studies ; Soil liquefaction ; Post-seismic studies ; Interseismic studies ; Volcanic unrest ; Pre-eruptive phase ; Eruptive phase ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations ; 04. Solid Earth::04.03. Geodesy::04.03.06. Measurements and monitoring ; 04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy ; 04. Solid Earth::04.03. Geodesy::04.03.09. Instruments and techniques ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 4
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    Recent slowdown and thinning of debris-covered glaciers in south-eastern Tibet (2017)
    Elsevier
    In:  EPIC3Earth and Planetary Science Letters, Elsevier, 464, pp. 95-102
    Details
    Publication Date: 2017-04-18
    Description: Recent large-scale remote sensing studies have shown that glacier mass loss in south-eastern Tibet, specifically in the eastern Nyainqêntanglha Range exceeds the average in High Asia. However, detailed studies at individual glaciers are scarce and the drivers behind the observed changes are poorly constrained to date. Employing feature tracking techniques on TerraSAR-X data for the periods 2008/2009, 2012/2013 and 2013/2014 we found measurable surface velocities through to the glacier terminus positions of five debris-covered glacier tongues. This is contrary to debris-covered glaciers in other parts of High Asia, where stagnant glacier tongues are common. Our feature tracking results for the 2013/2014 period suggest an average deceleration of 51% when compared with published Landsat velocities for the period 1999/2003. Further, we estimated surface elevation changes for the five glaciers from recently released one arc second resolution elevation data obtained during the Shuttle Radar Topography Mission in 2000 and an interferometrical derived TanDEM-X elevation model for the year 2014. With an average rate of −0.83 ± 0.57 m a^-1 we confirm strong surface lowering in the region, despite the widely discussed insulation effect of debris cover. Beside the influence of thermokarst processes and delayed response times of debris-covered glaciers, we highlight that abundant monsoonal summer rainfall might contribute significantly to the pronounced negative mass balances in the study region.
    Repository Name: EPIC Alfred Wegener Institut
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  • 5
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    How representative are dissolved organic matter (DOM) extracts? A comprehensive study of sorbent selectivity for DOM isolation (2017)
    Elsevier
    In:  EPIC3Water Research, Elsevier, 116, pp. 316-323
    Details
    Publication Date: 2017-04-10
    Description: Solid phase extraction (SPE) has become a widespread method for isolating dissolved organic matter (DOM) of diverse origin such as fresh and marine waters. This study investigated the DOM extraction selectivity of 24 commercially available SPE sorbents under identical conditions (pH = 2, methanol elution) on the example of Suwannee River (SR) water and North Sea (NS) water by using DOC analysis and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Proton nuclear magnetic resonance (1H NMR) spectroscopy was employed to assess leaching behavior, and HLB sorbent was found to leach substantially, among others. Variable DOC recoveries observed for SR DOM and NS DOM were primarily caused by the respective molecular composition, with subordinated and heterogeneous contributions of relative salinity. Scatter of average H/C and O/C elemental ratios and gross alignment in mass-edited H/C ratios according to five established coarse SPE characteristics was near identical for SR DOM and NS DOM. FTMS-based principal component analysis (PCA) provided essentially analogous alignment of SR DOM and NS DOM molecular compositions according to the five established groups of SPE classification, and corroborated the sorption-mechanism-based selectivity of DOM extraction in both cases. Evaluation of structural blanks and leaching of SPE cartridges requires NMR spectroscopy because FT-ICR mass spectrometry alone will not reveal inconspicuous displacements of continual bulk signatures caused by leaching of SPE resin constituents.
    Repository Name: EPIC Alfred Wegener Institut
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  • 6
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    Sub-seasonal thaw slump mass wasting is not consistently energy limited at the landscape scale (2017)
    Copernicus
    In:  EPIC3The Cryosphere Discussions, Copernicus, 2017, pp. 1-24
    Details
    Publication Date: 2017-08-30
    Description: Predicting future thaw slump activity requires a sound understanding of the atmospheric drivers and geomorphic controls on mass wasting across a range of time scales. On sub-seasonal time scales, sparse measurements indicate that mass wasting at active slumps is often limited by the energy available for melting ground ice, but other factors such as rainfall or the formation of an insulating veneer may also be relevant. To study the sub-seasonal drivers, we derive topographic changes from single-pass radar interferometric data acquired by the TanDEM-X satellite (12 m resolution). The high vertical precision (around 30 cm), frequent observations (11 days) and large coverage (5000 km2) allow us to track volume losses as drivers such as the available energy change during summer in two study regions. We find that thaw slumps in the Tuktoyaktuk coastlands, Canada, are not energy limited in June, as they undergo limited mass wasting (height loss of around 0 cm/day) despite the ample available energy, indicating the widespread presence of an insulating snow or debris veneer. Later in summer, height losses generally increase (around 3 cm/day), but they do so in distinct ways. For many slumps, mass wasting tracks the available energy, a temporal pattern that is also observed at coastal yedoma cliffs on the Bykovsky Peninsula, Russia. However, the other two common temporal trajectories are asynchronous with the available energy, as they track strong precipitation events or show a sudden speed-up in late August, respectively. The observed temporal patterns are poorly related to slump characteristics like the slump area. The contrasting temporal behaviour of nearby thaw slumps highlights the importance of complex local and temporally varying controls on mass wasting.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , notRev , info:eu-repo/semantics/article
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  • 7
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    The crustal structure of Beira High, central Mozambique—Combined investigation of wide-angle seismic and potential field data (2016)
    Elsevier
    In:  EPIC3Tectonophysics, Elsevier, 683, pp. 233-254, ISSN: 00401951
    Details
    Publication Date: 2018-12-19
    Description: The timing and geometry of the initial Gondwana break-up between Africa and East Antarctica is still poorly known due to missing information about the continent-ocean boundaries along the rifted margins. In this context, the Beira High off central Mozambique forms a critical geological feature of uncertain crustal fabric. Based on new wide-angle seismic and potential field data across Beira High a P-wave velocity model, supported by amplitude and gravity modelling, provides constraints on the crustal composition of this area. In the Mozambique Basin mainly normal oceanic crust of 5.5–7 km thickness with velocities of 6.5–7.0 km/s in the lower crust is present. A sharp transition towards Beira High marks the continent-ocean boundary. Here the crust thickens to 23 km at maximum. A small velocity-depth gradient and a constant increase in velocity with basal velocities of maximum 7.0 km/s are in good agreement with typical velocities of continental crust and continental fragments. The density model indicates the existence of felsicmaterial in greater depths and supports a fabric of stretched, but highly intruded continental crust below Beira High. A gradual decrease in crustal thickness characterizes the transition towards the Mozambican shelf area. Here, in the Zambezi Delta Depression 12 km of sediments cover the underlying 7 km thick crust. The presence of a high-velocity lower crustal body with velocities of 7.1–7.4 km/s indicates underplated, magmatic material in this part of the profile. However, the velocity structure in the shelf area allows no definite interpretation because of the experimental setup. Thus, the crustal nature below the Zambezi Delta and consequently the landward position of the continentocean boundary remains unknown. The difference in stretching below the margins of Beira High suggests the presence of different thinning directions and a rift jump during the early rifting stage.
    Repository Name: EPIC Alfred Wegener Institut
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  • 8
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    2014 iAREA campaign on aerosol in Spitsbergen Part 1: Study of physical and chemical properties (2016)
    Elsevier
    In:  EPIC3Atmospheric Environment, Elsevier, (140), pp. 150-166
    Details
    Publication Date: 2016-07-06
    Description: This paper presents the results of measurements of aerosol physical and chemical properties during iAREA2014 campaign that took place on Svalbard between 15th of Mar and 4th of May 2014. With respect to field area, the experiment consisted of two sites: NyeÅlesund (78�550N, 11�560E) and Longyearbyen (78�130N, 15�330E) with further integration of Aerosol Robotic Network (AERONET) station in Hornsund (77�000N, 15�330E). The subject of this study is to investigate the inesitu, passive and active remote sensing observations as well as numerical simulations to describe the temporal variability of aerosol singleescattering properties during spring season on Spitsbergen. The retrieval of the data indicates several event days with enhanced singleescattering properties due to the existence of sulphate and additional seaesalt load in the atmosphere which is possibly caused by relatively high wind speed. Optical results were confirmed by numerical simulations made by the GEMeAQ model and by chemical observations that indicated up to 45% contribution of the seaesalt to a PM10 total aerosol mass concentration. An agreement between the in-situ optical and microphysical properties was found, namely: the positive correlation between aerosol scattering coefficient measured by the nephelometer and effective radius obtained from laser aerosol spectrometer as well as negative correlation between aerosol scattering coefficient and the Ångstrom exponent indicated that slightly larger particles dominated during special events. The inesitu surface observations do not show any significant enhancement of the absorption coefficient as well as the black carbon concentration which might occur during spring. All of extensive singleescattering properties indicate a diurnal cycle in Longyearbyen, where 21:00e5:00 data stays at the background level, however increasing during the day by the factor of 3e4. It is considered to be highly connected with local emissions originating in combustion, traffic and harbour activities. On the other hand, no daily fluctuations in NyeÅlesund are observed. Mean values in NyeÅlesund are equal to 8.2, 0.8 Mm�1 and 103 ng/m3 for scattering, absorption coefficients and black carbon concentration; however in Longyearbyen (only data from 21:00e05:00 UTC) they reach 7.9, 0.6 Mm�1 as well as 83 ng/ m3 respectively. Overall, the spring 2014 was considerably clean and seaesalt was the major aerosol component
    Repository Name: EPIC Alfred Wegener Institut
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  • 9
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    Size distributions of coastal ocean suspended particulate inorganic matter: Amorphous silica and clay minerals and their dynamics (2017)
    Elsevier
    In:  EPIC3Estuarine, Coastal and Shelf Science, Elsevier, 189, pp. 243-251
    Details
    Publication Date: 2017-03-28
    Description: Particulate inorganic matter (PIM) is a key component in estuarine and coastal systems and plays a critical role in trace metal cycling. Better understanding of coastal dynamics and biogeochemistry requires improved quantification of PIM in terms of its concentration, size distribution, and mineral species composition. The angular pattern of light scattering contains detailed information about the size and composition of particles. These volume scattering functions(VSFs) were measured in Mobile Bay, Alabama, USA, a dynamic, PIM dominated coastal environment. From measured VSFs, we determined through inversion the particle size distributions (PSDs) of major components of PIM, amorphous silica and clay minerals. An innovation here is the extension of our reported PSDs significantly into the submicron range. The PSDs of autochthonous amorphous silica exhibit two unique features: a peak centered at about 0.8 μm between 0.2 and 4 μm and a very broad shoulder essentially extending from 4 μm to 〉100 μm. With an active and steady particle source from blooming diatoms, the shapes of amorphous silica PSDs for sizes 〈 10 μm varied little across the study area, but showed more particles of sizes 〉 10 μm inside the bay, likely due to wind-induced resuspension of larger frustules that have settled. Compared to autochthonous amorphous silica, the allochthonous clay minerals are denser and exhibit relatively narrower PSDs with peaks located between 1 and 4 μm. Preferential settling of larger mineral particles as well as the smaller but denser illite component further narrowed the size distributions of clay minerals as they were being transported outside the bay. The derived PSDs also indicated a very dynamic situation in Mobile Bay relative to the cold weather front that passed through during the experiment. With northerly winds of speeds up to 15 m s-1, both amorphous silica and clay minerals showed a dramatic increase in concentration and broadening in size distribution outside the exit of the barrier islands, indicative of wind-induced resuspension and subsequent advection of particles out of Mobile Bay. While collectively recognized as the PIM, amorphous silica and clay minerals, as shown in this study, possess very different size distributions. Considering how differences in PSDs and the associated particle areas will effect differences in sorption/desorption properties of these components, the results also demonstrate the potential of applying VSF-inversion in studying biogeochemistry in the estuarine-coastal ocean system.
    Repository Name: EPIC Alfred Wegener Institut
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  • 10
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    Oxygenated volatile organic carbon in the western Pacific convective centre: ocean cycling, air–sea gas exchange and atmospheric transport. (2017)
    Copernicus
    In:  EPIC3Atmos. Chem. Phys. Discuss., Copernicus, acp-20, ISSN: 1680-7375
    Details
    Publication Date: 2017-11-06
    Description: A suite of oxygenated volatile organic compounds (OVOCs – acetaldehyde, acetone, propanal, butanal and butanone) were measured concurrently in the surface water and atmosphere of the South China Sea and Sulu Sea in November 2011. A strong correlation was observed between all OVOC concentrations in the surface seawater along the entire cruise track, except for acetaldehyde, suggesting similar sources and sinks in the surface ocean. Additionally, several phytoplankton groups, such as haptophytes or pelagophytes, were also correlated to all OVOCs indicating that phytoplankton may be an important source for marine OVOCs in the South China and Sulu Seas. Humic and protein like fluorescent dissolved organic matter (FDOM) components seemed to be additional precursors for butanone and acetaldehyde. The atmospheric OVOC mixing ratios were relative high compared with literature values, suggesting the coastal region of North Borneo as a local hot spot for atmospheric OVOCs. The flux of atmospheric OVOCs was largely into the ocean for all 5 gases, with a few important exceptions near the coast of Borneo. The calculated amount of OVOCs entrained into the ocean seemed to be an important source of OVOCs to the surface ocean. When the fluxes were out of the ocean, marine OVOCs were found to be enough to control the local measured OVOC distribution in the atmosphere. Based on our model calculations, at least 0.4 ppb of marine derived acetone and butanone can reach the upper troposphere, where they may have an important influence on hydrogen oxide radical formation over the western Pacific Ocean.
    Repository Name: EPIC Alfred Wegener Institut
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  • 11
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    The Extrapolar SWIFT model (version 1.0): fast stratospheric ozone chemistry for global climate models (2017)
    Copernicus
    In:  EPIC3Geoscientific Model Development, Copernicus, 11, pp. 753-769
    Details
    Publication Date: 2018-03-28
    Description: The Extrapolar SWIFT model is a fast ozone chemistry scheme for interactive calculation of the extrapolar stratospheric ozone layer in coupled general circulation models (GCMs). In contrast to the widely used prescribed ozone, the SWIFT ozone layer interacts with the model dynamics and can respond to atmospheric variability or climatological trends. The Extrapolar SWIFT model employs a repro-modelling approach, where algebraic functions are used to approximate the numerical output of a full stratospheric chemistry and transport model (ATLAS). The full model solves a coupled chemical differential equations system with 55 initial and boundary conditions (mixing ratio of various chemical species and atmospheric parameters). Hence the rate of change of ozone over 24  h is a function of 55 variables. Using covariances between these variables, we can find linear combinations in order to reduce the parameter space to the following nine basic variables: latitude, pressure altitude, temperature, local ozone column, mixing ratio of ozone and of the ozone depleting families (Cly, Bry, NOy and HOy). We will show that these 9 variables are sufficient to characterize the rate of change of ozone. An automated procedure fits a polynomial function of fourth degree to the rate of change of ozone obtained from several simulations with the ATLAS model. One polynomial function is determined per month which yields the rate of change of ozone over 24 h. A key aspect for the robustness of the Extrapolar SWIFT model is to include a wide range of stratospheric variability in the numerical output of the ATLAS model, also covering atmospheric states that will occur in a future climate (e.g. temperature and meridional circulation changes or reduction of stratospheric chlorine loading). For validation purposes, the Extrapolar SWIFT model has been integrated into the ATLAS model replacing the full stratospheric chemistry scheme. Simulations with SWIFT in ATLAS have proven that the systematic error is small and does not accumulate during the course of a simulation. In the context of a 10 year simulation, the ozone layer, simulated by SWIFT, shows a stable annual cycle, with inter-annual variations comparable to the ATLAS model. The application of Extrapolar SWIFT requires the evaluation of polynomial functions with 30–100 terms. Nowadays, computers can calculate such polynomial functions at thousands of model grid points in seconds. SWIFT provides the desired numerical efficiency and computes the ozone layer 104 times faster than the chemistry scheme in the ATLAS CTM.
    Repository Name: EPIC Alfred Wegener Institut
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  • 12
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    Can preferred atmospheric circulation patterns over the North-Atlantic-Eurasian region be associated with arctic sea ice loss? (2017)
    Elsevier
    In:  EPIC3Polar Scienece, Elsevier, 14, pp. 9-20
    Details
    Publication Date: 2019-01-31
    Description: n the framework of atmospheric circulation regimes, we study whether the recent Arctic sea ice loss and Arctic Amplification are associated with changes in the frequency of occurrence of preferred atmospheric circulation patterns during the extended winter season from December to March. To determine regimes we applied a cluster analysis to sea-level pressure fields from reanalysis data and output from an atmospheric general circulation model. The specific set up of the two analyzed model simulations for low and high ice conditions allows for attributing differences between the simulations to the prescribed sea ice changes only. The reanalysis data revealed two circulation patterns that occur more frequently for low Arctic sea ice conditions: a Scandinavian blocking in December and January and a negative North Atlantic Oscillation pattern in February and March. An analysis of related patterns of synoptic-scale activity and 2 m temperatures provides a synoptic interpretation of the corresponding large-scale regimes. The regimes that occur more frequently for low sea ice conditions are resembled reasonably well by the model simulations. Based on those results we conclude that the detected changes in the frequency of occurrence of large-scale circulation patterns can be associated with changes in Arctic sea ice conditions.
    Repository Name: EPIC Alfred Wegener Institut
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  • 13
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    Winter sea ice export from the Laptev Sea preconditions the local summer sea ice cover and fast ice decay (2017)
    Copernicus
    In:  EPIC3The Cryosphere, Copernicus, 11(5), pp. 2383-2391
    Details
    Publication Date: 2017-10-24
    Description: Ice retreat in the eastern Eurasian Arctic is a consequence of atmospheric and oceanic processes and regional feedback mechanisms acting on the ice cover, both in winter and summer. A correct representation of these processes in numerical models is important, since it will improve predictions of sea ice anomalies along the Northeast Passage and beyond. In this study, we highlight the importance of winter ice dynamics for local summer sea ice anomalies in thickness, volume and extent. By means of airborne sea ice thickness surveys made over pack ice areas in the south-eastern Laptev Sea, we show that years of offshore-directed sea ice transport have a thinning effect on the late-winter sea ice cover. To confirm the preconditioning effect of enhanced offshore advection in late winter on the summer sea ice cover, we perform a sensitivity study using a numerical model. Results verify that the preconditioning effect plays a bigger role for the regional ice extent. Furthermore, they indicate an increase in volume export from the Laptev Sea as a consequence of enhanced offshore advection, which has far-reaching consequences for the entire Arctic sea ice mass balance. Moreover we show that ice dynamics in winter not only preconditions local summer ice extent, but also accelerate fast-ice decay.
    Repository Name: EPIC Alfred Wegener Institut
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  • 14
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    Iron partitioning during LOHAFEX: Copepod grazing as a major driver for iron recycling in the Southern Ocean (2017)
    Elsevier
    In:  EPIC3Marine Chemistry, Elsevier, 196, pp. 148-161
    Details
    Publication Date: 2018-04-13
    Description: eddy located along the Antarctic Polar Front in the Atlantic sector of the Southern Ocean. Mixed layer (ML) waters were characterized by high nitrate (~20 μM), low dissolved iron (DFe ~0.2 nM) and low silicate concentrations (below 1 μM) restricting diatom growth. Upon initial fertilization, chlorophyll-a doubled during the first two weeks and stabilized thereafter, despite a second fertilization on day 21, due to an increase in grazing pressure. Biomass at the different trophic levels was mostly comprised of small autotrophic flagellates, the large copepod Calanus simillimus and the amphipod Themisto gaudichaudii. The downward flux of particulate material comprised mainly copepod fecal pellets that were remineralized in the upper 150 m of the water column with no significant deeper export. showed a greater variability (ranging from 0.3 to 1.3 nM) without a clear vertical pattern. Particulate iron concentrations (measured after 2 months at pH 1.4) decreased with time and showed a vertical pattern that indicated an important non-biogenic component at the bottom of the mixed layer. In order to assess the contribution of copepod grazing to iron cycling we used two different approaches: first, we measured for the first time in a field experiment copepod fecal pellet concentrations in the water column together with the iron content per pellet, and second, we devised a novel analytical scheme based on a two-step leaching protocol to estimate the contribution of copepod fecal pellets to particulate iron in the water column. Analysis of the iron content of isolated fecal pellets from C. simillimus showed that after the second fertilization, the iron content per fecal pellet was ~5 fold higher if the copepod had been captured in fertilized waters. We defined a new fraction termed leachable iron (pH 2.0) in 48 h (LFe48h) that, for the conditions during LOHAFEX, was shown to be an excellent proxy for the concentration of iron contained in copepod fecal pellets. We observed that, as a result of the second fertilization, iron accumulated in copepod fecal pellets and remained high at one third of the total iron stock in the upper 80 m. We hypothesize that our observations are due to a combination of two biological processes. First, phagotrophy of iron colloids freshly formed after the second fertilization by the predominant flagellate community resulted in higher Fe:C ratios per cell that, via grazing, lead to iron enrichment in copepod fecal pellets in fertilized waters. Second, copepod coprophagy could explain the rapid recycling of particulate iron in the upper 100–150 m, the accumulation of LFe48h in the upper 80 m after the second fertilization and provided the iron required for the maintenance of the LOHAFEX bloom for many weeks. Our results provide the first quantitative evidence of the major ecological relevance of copepods and their fecal products in the cycling of iron in silicate depleted areas of the Southern Ocean.
    Repository Name: EPIC Alfred Wegener Institut
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  • 15
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    Scaling-up permafrost thermal measurements in western Alaska using an ecotype approach (2016)
    Copernicus
    In:  EPIC3The Cryosphere, Copernicus, 10(5), pp. 2517-2532, ISSN: 1994-0424
    Details
    Publication Date: 2020-09-06
    Description: Permafrost temperatures are increasing in Alaska due to climate change and in some cases permafrost is thawing and degrading. In areas where degradation has already occurred the effects can be dramatic, resulting in changing ecosystems, carbon release, and damage to infrastructure. However, in many areas we lack baseline data, such as subsurface temperatures, needed to assess future changes and potential risk areas. Besides climate, the physical properties of the vegetation cover and subsurface material have a major influence on the thermal state of permafrost. These properties are often directly related to the type of ecosystem overlaying permafrost. In this paper we demonstrate that classifying the landscape into general ecotypes is an effective way to scale up permafrost thermal data collected from field monitoring sites. Additionally, we find that within some ecotypes the absence of a moss layer is indicative of the absence of near-surface permafrost. As a proof of concept, we used the ground temperature data collected from the field sites to recode an ecotype land cover map into a map of mean annual ground temperature ranges at 1 m depth based on analysis and clustering of observed thermal regimes. The map should be useful for decision making with respect to land use and understanding how the landscape might change under future climate scenarios.
    Repository Name: EPIC Alfred Wegener Institut
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  • 16
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    The evolution of a thermokarst-lake landscape: Late Quaternary permafrost degradation and stabilization in interior Alaska (2016)
    Elsevier
    In:  EPIC3Sedimentary Geology, Elsevier, 340, pp. 3-14, ISSN: 00370738
    Details
    Publication Date: 2016-09-24
    Description: Thermokarst processes characterize a variety of ice-rich permafrost terrains and often lead to lake formation. The long-term evolution of thermokarst landscapes and the stability and longevity of lakes depend upon climate, vegetation and ground conditions, including the volume of excess ground ice and its distribution. The current lake status of thermokarst-lake landscapes and their future trajectories under climatewarming are better understood in the light of their long-term development. We studied the lake-rich southern marginal upland of the Yukon Flats (northern interior Alaska) using dated lake-sediment cores, observations of river-cut exposures, and remotely-sensed data. The region features thick (up to 40 m)Quaternary deposits (mainly loess) that contain massive ground ice. Two of three studied lakes formed ~11,000–12,000 cal yr BP through inferred thermokarst processes, and fire may have played a role in initiating thermokarst development. From ~9000 cal yr BP, all lakes exhibited steady sedimentation, and pollen stratigraphies are consistentwith regional patterns. The current lake expansion rates are low (0 to b7 cmyr−1 shoreline retreat) compared with other regions (~30 cm yr−1 or more). This thermokarst lake-rich region does not showevidence of extensive landscape lowering by lake drainage, nor of multiple lake generations within a basin. However, LiDAR images reveal linear “corrugations” (N5 m amplitude), deep thermo-erosional gullies, and features resembling lake drainage channels, suggesting that highly dynamic surface processes have previously shaped the landscape. Evidently, widespread early Holocene permafrost degradation and thermokarst lake initiation were followed by lake longevity and landscape stabilization, the latter possibly related to establishment of dense forest cover. Partial or complete drainage of three lakes in 2013 reveals that there is some contemporary landscape dynamism. Holocene landscape evolution in the study area differs from that described from other thermokarst-affected regions; regional responses to future environmental change may be equally individualistic.
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  • 17
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    Facies analysis of yedoma thermokarst lakes on the northern Seward Peninsula, Alaska (2016)
    Elsevier
    In:  EPIC3Sedimentary Geology, Elsevier, 340, pp. 25-37, ISSN: 00370738
    Details
    Publication Date: 2016-09-23
    Description: Thermokarst lakes develop as a result of the thaw and collapse of ice-rich, permanently frozen ground (permafrost). Of particular sedimentological importance are thermokarst lakes forming in late Pleistocene icy silt (yedoma),which dramatically alter the land surface by lowering surface elevation and redistributing upland sediment into lower basins. Our study provides the first description of yedoma thermokarst lake sedimentology based on the crossbasin sampling of an existing lake. We present lake sediment facies descriptions based on data from sediment cores from two thermokarst lakes of medium depth, Claudi and Jaeger (informal names), which formed in previously non thermokarst-affected upland yedoma on the northern Seward Peninsula, Alaska. We identify four prominent facies using sedimentological, biogeochemical, and macrofossil indicators: a massive silt lacking aquatic macrofossils and other aquatic indicators situated below a sub-lacustrine unconformity (Facies 1); two basal deposits: interbedded organic silt and chaotic silt (Facies 2–3); and a silt-rich mud (Facies 4). Facies 1 is interpreted as yedoma that has thawed during lake formation. Facies 3 formed adjacent to the margin due to thaw and collapse events from the lake shore. Material from Facies 3 was reworked by wave action to form Facies 2 in a medium energy margin environment. Facies 4 formed in a lower energy environment toward the lake basin center. This facies classification and description should enhance our ability (i) to interpret the spatial and temporal development of lakes and (ii) to reconstruct long-term patterns of landscape change.
    Repository Name: EPIC Alfred Wegener Institut
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  • 18
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    Oxidative balance in macroalgae from Antarctic waters. Possible role of Fe (2017)
    Elsevier
    In:  EPIC3Journal of Experimental Marine Biology and Ecology, Elsevier, 486, pp. 379-386
    Details
    Publication Date: 2016-11-22
    Description: The hypothesis of this work was that exposure to diverse abiotic factors in two sites with different sediment and iron input (Peñón de Pesca: low impact; Island D: high impact, both areas in Potter Cove, King George Island, Antarctica) affects the physiological and oxidative profile of Gigartina skottsbergii and Himantothallus grandifolius. Daily metabolic carbon balance was significantly lower in both macroalgae from Island D compared to Peñón de Pesca. Lipid radical (LRradical dot) content was significantly higher in G. skottsbergii collected from Island D compared to Peñón de Pesca. In contrast, H. grandifolius showed significantly lower values in Island D compared to Peñón de Pesca. The β-carotene (β-C) content was significantly lower in G. skottsbergii from Island D compared to Peñón de Pesca, and the ratio LRradical dot/β-C showed a 6-fold increase in Island D samples compared to Peñón de Pesca. On the other hand, β-C content in H. grandifolius showed no significant differences between both areas. The LRradical dot/β-C content ratio in this alga was significantly lower (26%) in Island D as compared to Peñón de Pesca. Total iron content was significantly higher in both macroalgae from Island D compared to samples from Peñón de Pesca. Results with G. skottsbergii suggested changes in the oxidative cellular balance, probably related to the higher environmental iron in Island D as compared to Peñón de Pesca. The species H. grandifolius seems to be better adapted to the environmental conditions especially through a higher antioxidant capacity to cope with oxidative stress.
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  • 19
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    Late quaternary climate, precipitation δ18O, and Indian monsoon variations over the Tibetan Plateau (2017)
    Elsevier
    In:  EPIC3Earth and Planetary Science Letters, Elsevier, 457, pp. 412-422, ISSN: 0012821X
    Details
    Publication Date: 2017-01-02
    Description: The Himalaya–Tibet orogen contains one of the largest modern topographic and climate gradients on Earth. Proxy data from the region provide a basis for understanding Tibetan Plateau paleo climate and paleo elevation reconstructions. Paleo climate model comparisons to proxy data compliment sparsely located data and can improve climate reconstructions. This study investigates temporal changes in precipitation, temperature and precipitation δ18O(δ18Op) over the Himalaya–Tibet from the Last Glacial Maximum (LGM) to present. We conduct a series of atmospheric General Circulation Model (GCM, ECHAM5-wiso) experiments at discrete time slices including a Pre-industrial (PI, Pre-1850 AD), Mid Holocene (MH, 6 ka BP) and LGM (21 ka BP) simulations. Model predictions are compared with existing proxy records. Model results show muted climate changes across the plateau during the MH and larger changes occurring during the LGM. During the LGM surface temperatures are ∼2.0–4.0◦C lower across the Himalaya and Tibet, and 〉5.0◦C lower at the northwest and northeast edge of the Tibetan Plateau. LGM mean annual precipitation is 200–600 mm/yr lower over on the Tibetan Plateau. Model and proxy data comparison shows a good agreement for the LGM, but large differences for the MH. Large differences are also present between MH proxy studies near each other. The precipitation weighted annual mean δ18Op lapse rate at the Himalaya is about 0.4h/km larger during the MH and 0.2h/km smaller during the LGM than during the PI. Finally, rainfall associated with the continental Indian monsoon (between 70◦E–110◦E and 10◦N–30◦N) is about 44% less in the LGM than during PI times. The LGM monsoon period is about one month shorter than in PI times. Taken together, these results document significant spatial and temporal changes in temperature, precipitation, and δ18Op over the last ∼21 ka. These changes are large enough to impact interpretations of proxy data and the intensity of the Indian monsoon.
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  • 20
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    Linking education and science to increase awareness of marine plastic litter - Distribution of plastic waste on beaches of the German Bight (2016)
    Elsevier
    In:  EPIC3Fate and Impact of Microplastics in Marine Ecosystems, Fate and Impact of Microplastics in Marine Ecosystems, Elsevier, 1 p., pp. 162-163, ISBN: 978-0-12-812271-6
    Details
    Publication Date: 2017-06-21
    Description: Since the 1950s more than 6.1 billion tons of plastics have been produced. It has been estimated that about 10% of this amount will be deposited long-term in theOceans. The problem is highlighted by several currentstudies using different environmental sampling protocols and analytical methods. Effects of this anthropogenic litter on the environment and organisms are heavily on debate, emphasizing the need to transfer this knowledge to young educated people and to fuel educational programs. The school lab OPENSEA at the Alfred-Wegener-Institute on Helgoland started a joint high school project on marine plastic litter in cooperation with the experts of the marine microplastics group at AWI to link science and education more closely. Based on the OSPAR protocol for beach monitoring of marine litter we developed an experimental set up focusing on sampling and identification of plastic litter on beaches, shores and in sediments in the course of the OPENSEA science and education program for grammar and high school scholars. This monitoring provides environmental data on marine plastic litter and will be integrated in a long term data monitoring program in the course of a citizen science study. In addition we plan to integrate also smaller plastic particles into the project. Fractionated sediment samples will be screened for particles 〉 0.5mm, which then will be analyzed by ATR-FT-IR. These educational activities, with a strong link to the latest science and to sophisticated technology will raise the awareness of younger people for the marine litter problematic. We aim at increasingtheir concerns after taking part in this program. We will present background information, sampling strategies, identification efforts and results based on this scholar science project.
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  • 21
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    Vast Quantities of Microplastics in Arctic Sea Ice—A Prime Temporary Sink for Plastic Litter and a Medium of Transport (2017)
    Elsevier
    In:  EPIC3Fate and Impact of Microplastics in Marine Ecosystems, MICRO 2016, Amsterdam, Elsevier, 2 p., pp. 75-76
    Details
    Publication Date: 2017-01-20
    Description: Although the Arctic covers 6% of our planet’s surface and plays a key role in the Earth’s climate it remains one of the least explored ecosystems. The global change induced decline of sea ice has led to increasing anthropogenic presence in the Arctic Ocean. Exploitation of its resources is already underway, and Arctic waters are likely important future shipping lanes as indicated by already increasing numbers of fishing vessels, cruise liners and hydrocarbon prospecting in the area over the past decade. Global estimates of plastic entering the oceans currently exceed results based on empirical evidence by up to three orders of magnitude highlighting that we have not yet identified some of the major sinks of plastic in our oceans. Fragmentation into microplastics could explain part of the discrepancy. Indeed, microplastics were identified from numerous marine ecosystems globally, including the Arctic. Here, we analysed horizons of ice cores from the western and eastern Fram Strait by focal plane array based micro-Fourier transform infrared spectroscopy to assess if sea ice is a sink of microplastic. Ice cores were taken from land-locked and drifting sea ice to distinguish between local entrainment of microplastics vs long-distance transport. Mean concentrations of 2 x 106 particles m-3 in pack ice and 6 x 105 particles m-3 in land-locked ice were detected (numbers of fibers will soon be added). Eleven different polymer types were identified; polyethylene (PE) was the most abundant one. Preliminary results from four further ice cores from the central Arctic range in a similar order but the microplastics composition was very different. Calculation of drift trajectories by back-tracking of the ice floes sampled indicates multiple source areas, which explains the differences in the microplastic composition. Preliminary analysis of snow samples taken from ice floes in the Fram Strait showed numerous fibers of yet unknown but most likely anthropogenic origin indicating atmospheric fallout as a possible pathway. Our results exceed concentrations from the North Pacific by several orders of magnitudes. This can be explained partly by the process of ice formation, during which (organic) particles tend to concentrate by 1-2 orders of magnitude compared with ambient seawater. However, the magnitude of the difference indicates that Arctic sea ice is a temporal sink for microplastics. Increasing quantities of small plastic litter items on the seafloor nearby, which is located in the marginal ice zone corroborate the notion that melting sea ice releases entrained plastic particles and that sea ice acts as a vector of transport both horizontally and vertically to underlying ecosystem compartments.
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  • 22
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    Automated Analysis of µFTIR Imaging Data for Microplastic Samples (2016)
    Elsevier
    In:  EPIC3Fate and Impact of Microplastics in Marine Ecosystems, Elsevier
    Details
    Publication Date: 2017-05-29
    Description: The pollution of the oceans with plastic particles smaller than 5 mm, called microplastics is moving into the focus of science and governments. To determine the amount of microplastics several steps are necessary, starting with the sampling, work up and finally analysis. Each step has its own challenges due to small size of the particles. For analysis the imaging with µFTIR microscopy is a powerful tool allowing the analysis of complete filters. Systematic screening for optimal conditions and filter materials have already been performed. This method has a high time demand regarding the measurement and data interpretation. While the measurement is performed mostly by the spectrometer, the interpretation has to be made by hand on the basis of false color images. To overcome the manual part we developed a novel approach based on the Bruker OPUS© Software to decrease the high time demand for the analysis of microplastics. With this approach it was possible to analyze measurement files from focal plane array (FPA) FTIR mapping containing up to 1.8 million single spectra. These spectra were compared with a database of different synthetic and natural polymers by various methods. By benchmark tests their performance was monitored with the focus on accuracy and data quality. After optimization high quality data was generated, which allowed image analysis. Based on these results an approach for image analysis was developed, giving information for the particle size distribution for each polymer type, particle distribution on the filter and polymer distribution for the particles. It was possible to collect all data with relative ease even for complex sample matrices. This approach has significantly decreased the time demand for the interpretation of FTIR-imaging data and increased the generated data quality.
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  • 23
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    PAPARA(ZZ)I: An open-source software interface for annotating photographs of the deep-sea (2017)
    Elsevier
    In:  EPIC3SoftwareX, Elsevier, 6, pp. 69-80, ISSN: 2352-7110
    Details
    Publication Date: 2017-03-06
    Repository Name: EPIC Alfred Wegener Institut
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  • 24
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    Dynamics of the Terra Nova Bay Polynya: The potential of multi-sensor satellite observations (2016)
    Elsevier
    In:  EPIC3Remote Sensing of Environment, Elsevier, 187, pp. 30-48, ISSN: 0034-4257
    Details
    Publication Date: 2017-01-20
    Description: Research on processes leading to formation, maintenance, and disappearance of polynyas in the Polar Regions benefits significantly from the use of different types of remote sensing data. The Sentinels of the European Space Agency (ESA), together with other satellite missions, provide a variety of data from different parts of the electromagnetic spectrum, at different spatial scales, and with different temporal resolutions. In a case study we demonstrate the advantage of merging data from different spaceborne instruments for analysing ice conditions and ice dynamics in and around the frequently occurring Terra Nova Bay Polynya (TNBP) in the Ross Sea in the Antarctic. Starting with a list of polynya parameters that are typically retrieved from satellite images, we assess the usefulness of different sensor types. On regional scales (several 100 km), passive microwave radiometers provide a view on the mutual influence of the three Ross Sea polynyas on sea ice drift and deformation patterns. Optical sensors with meter-scale resolution, on the other hand, allow very localized analyses of different polynya zones. The combination of different ranges of the electromagnetic spectrum is essential for recognition and classification of ice types and structures. Radar images together with data from thermal infrared sensors, operated at tens to hundreds of meters resolution, improve the separation of the outlet zone of the polynya from the adjacent pack ice. The direct comparison of radar and passive microwave images reveals the visibility of deformed ice zone in the latter. A sequence of radar images was employed to retrieve ice drift around the TNB, which allows analysing the temporal changes of the polynya area and the extension and structure of the outlet zone as well as ice movements and deformation that are influenced by the katabatic winds.
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  • 25
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    Mapping of the air–sea CO2 flux in the Arctic Ocean and its adjacent seas: Basin-wide distribution and seasonal to interannual variability (2016)
    Elsevier
    In:  EPIC3Polar Science, Elsevier, 10(3), pp. 323-334, ISSN: 18739652
    Details
    Publication Date: 2016-10-10
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  • 26
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    Temporal changes in ventilation and the carbonate system in the Atlantic sector of the Southern Ocean (2017)
    Elsevier
    In:  EPIC3Deep Sea Research Part II, Elsevier, 138, pp. 26-38, ISSN: 09670645
    Details
    Publication Date: 2017-05-03
    Repository Name: EPIC Alfred Wegener Institut
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  • 27
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    Ocean Current Changes (2016)
    Elsevier
    In:  EPIC3Climate Change, Ocean Current Changes, Amsterdam, Elsevier, pp. 253-269
    Details
    Publication Date: 2016-12-05
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  • 28
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    Contamination of our oceans by plastics (2017)
    Elsevier
    In:  EPIC3Reference Module in Earth Systems and Environmental Sciences, Elsevier
    Details
    Publication Date: 2017-02-14
    Description: Vast quantities of plastics are accumulating in the oceans. At sea, plastics interact with marine biota often with deleterious consequences for organisms and habitats. As users of marine food resources and ecosystem services humans are also affected by marine plastic litter. Economic, social and health implications necessitate decisive action to manage this growing environmental problem at a global scale. Accordingly, legislative and technological instruments have been implemented to reduce the amounts of marine plastic debris. Promising strategies to reduce the human plastic footprint in the oceans must involve the minimization of plastic discharges into the marine environment.
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  • 29
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    LITTERBASE: An Online Portal for Marine Litter and Microplastics and Their Implications for Marine Life (2017)
    Elsevier
    In:  EPIC3Fate and Impact of Microplastics in Marine Ecosystems, MICRO 2016, Amsterdam, Elsevier, 2 p., pp. 106-107
    Details
    Publication Date: 2017-01-20
    Description: For many years, the pollution of the oceans with marine litter received only little attention from the public although the global plastic production has grown steadily. However, since the “discovery” of the oceanic garbage patches and microplastics the littering of the oceans has become a hot topic, which is reflected in strong recent increases in the number of publications. Despite growing research efforts many questions remain unanswered and the new wealth of information does not readily transpire to the general public, which is left unsettled. For example, it is still unclear what the overall extent of ocean pollution is, or how the enormous amounts of oceanic plastics affect marine life and ecosystems. To overcome this uncertainty and make best use of the existing knowledge, we currently develop an online portal for marine litter and microplastic pollution named LITTERBASE. As of early 2017, LITTERBASE will provide access to the current state of understanding of marine litter and microplastics to the general public and stakeholders. Published records of marine litter and microplastics and their impact on marine life will be compiled in a database. The regularly updated information will be displayed in distribution maps and other graphs in an interactive online portal. In the long run, data from citizen scientists may also be integrated into these infographs.
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  • 30
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    On the warm inflow at the eastern boundary of the Weddell Gyre (2016)
    Elsevier
    In:  EPIC3Deep Sea Research Part I: Oceanographic Research Papers, Elsevier, 107, pp. 70-81
    Details
    Publication Date: 2019-08-19
    Description: The Weddell Sea plays an important role for the global oceans and climate by being one of the biggest production and export areas of Antarctic Bottom Water (AABW). Circumpolar Deep Water (CDW) enters the Weddell Gyre (WG) at its eastern boundary. Then called Warm Deep Water (WDW), it is a major contributor to the formation of deep and bottom waters due to ocean-ice shelf interactions in the southern and soutwestern Weddell Sea. Hydrographic data collected between 0 and 30°E on the RV Polarstern cruise ANT XX/2 reveals a two-core structure for the eastern inflow of warm water at roughly 20°E but not further downstream at the Greenwich meridian (GM). Model results and climatological fields suggest that the two cores represent two separate modes of warm inflow. One mode is driven by eddy mixing in the northeastern corner of the WG and the other one is an advective mode, forming the southern branch of the inflow which extends beyond 30°E before turning westward. Both pathways are likely to carry waters from different origins within the Antarctic Circumpolar Current (ACC), where more ventilated CDW is found at the Southern Boundary (SB) compared to the centre. The southern route shows considerable interannual variability in the model. A variable inflow of two types of CDW together with admixed recirculated and cooler waters from the Weddell Sea can potentially contribute to the observed variability and warming trend of WDW over the last decade at the GM.
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  • 31
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    Antarctic climate variability on regional and continental scales over the last 2000 years (2017)
    Copernicus
    In:  EPIC3Climate of the Past, Copernicus, 13(11), pp. 1609-1634, ISSN: 1814-9332
    Details
    Publication Date: 2017-12-19
    Description: Climate trends in the Antarctic region remain poorly characterized, owing to the brevity and scarcity of direct climate observations and the large magnitude of interannual to decadal-scale climate variability. Here, within the framework of the PAGES Antarctica2k working group, we build an enlarged database of ice core water stable isotope records from Antarctica, consisting of 112 records. We produce both unweighted and weighted isotopic (δ18O) composites and temperature reconstructions since 0 CE, binned at 5- and 10-year resolution, for seven climatically distinct regions covering the Antarctic continent. Following earlier work of the Antarctica2k working group, we also produce composites and reconstructions for the broader regions of East Antarctica, West Antarctica and the whole continent. We use three methods for our temperature reconstructions: (i) a temperature scaling based on the δ18O–temperature relationship output from an ECHAM5-wiso model simulation nudged to ERA-Interim atmospheric reanalyses from 1979 to 2013, and adjusted for the West Antarctic Ice Sheet region to borehole temperature data, (ii) a temperature scaling of the isotopic normalized anomalies to the variance of the regional reanalysis temperature and (iii) a composite-plus-scaling approach used in a previous continent-scale reconstruction of Antarctic temperature since 1 CE but applied to the new Antarctic ice core database. Our new reconstructions confirm a significant cooling trend from 0 to 1900 CE across all Antarctic regions where records extend back into the 1st millennium, with the exception of the Wilkes Land coast and Weddell Sea coast regions. Within this long-term cooling trend from 0 to 1900 CE, we find that the warmest period occurs between 300 and 1000 CE, and the coldest interval occurs from 1200 to 1900 CE. Since 1900 CE, significant warming trends are identified for the West Antarctic Ice Sheet, the Dronning Maud Land coast and the Antarctic Peninsula regions, and these trends are robust across the distribution of records that contribute to the unweighted isotopic composites and also significant in the weighted temperature reconstructions. Only for the Antarctic Peninsula is this most recent century-scale trend unusual in the context of natural variability over the last 2000 years. However, projected warming of the Antarctic continent during the 21st century may soon see significant and unusual warming develop across other parts of the Antarctic continent. The extended Antarctica2k ice core isotope database developed by this working group opens up many avenues for developing a deeper understanding of the response of Antarctic climate to natural and anthropogenic climate forcings. The first long-term quantification of regional climate in Antarctica presented herein is a basis for data–model comparison and assessments of past, present and future driving factors of Antarctic climate.
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  • 32
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    Short-term variability in late Holocene sea ice cover on the East Greenland Shelf and its driving mechanisms (2017)
    Elsevier
    In:  EPIC3Palaeogeography, Palaeoclimatology, Palaeoecology, Elsevier, 485, pp. 336-350
    Details
    Publication Date: 2018-02-11
    Description: Arctic sea ice is a critical component of the climate system as it influences the albedo, heat, moisture and gas exchange between ocean and atmosphere as well as the ocean's salinity. An ideal location to study natural sea ice variability during pre-industrial times is the East Greenland Shelf that underlies the East Greenland Current (EGC), the main route of Arctic sea ice and freshwaters from the Arctic Ocean into the northern North Atlantic. Here, we present a new high-resolution biomarker record from the East Greenland Shelf (73°N), which provides new insights into the sea ice variability and accompanying phytoplankton productivity over the past 5.2 kyr. Our IP25 based sea ice reconstructions and the inferred PIP25 index do not reflect the wide-spread late Holocene Neoglacial cooling trend that follows the decreasing solar insolation pattern, which we relate to the strong influence of the polar EGC on the East Greenland Shelf and interactions with the adjacent fjord throughout the studied time interval. However, our reconstructions reveal several oscillations with increasing/decreasing sea ice concentrations that are linked to the known late Holocene climate cold/warm phases, i.e. the Roman Warm Period, Dark Ages Cold Period, Medieval Climate Anomaly and Little Ice Age. The observed changes seem to be connected to general ocean atmosphere circulation changes, possibly related to North Atlantic Oscillation and Atlantic Multidecadal Oscillation regimes. Furthermore, we identify a cyclicity of 73–74 years in sea ice algae and phytoplankton productivity over the last 1.2 kyr, which may indicate a connection to Atlantic Multidecadal Oscillation mechanisms.
    Repository Name: EPIC Alfred Wegener Institut
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  • 33
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    Organic Fe speciation in the Eurasian Basins of the Arctic Ocean and its relation to terrestrial DOM (2017)
    Elsevier
    In:  EPIC3Marine Chemistry, Elsevier, 197, pp. 11-25, ISSN: 03044203
    Details
    Publication Date: 2017-12-17
    Description: The bio-essential trace metal iron (Fe) has poor inorganic solubility in seawater, and therefore dissolution is dependent on organic complexation. The Arctic Ocean is subject to strong terrestrial influences which contribute to organic solubility of Fe, particularly in the surface. These influences are subject to rapid changes in the catchments of the main contributing rivers. Here we report concentrations and binding strengths of Fe-binding organic ligands in relation to spectral properties of Dissolved Organic Matter (DOM) and concentrations of humic substances. Full-depth profiles of Fe and Fe-binding organic ligands were measured for 11 stations, good agreement to previous studies was found with ligand concentrations between 0.9 and 2.2 equivalent nM of Fe (Eq. nM Fe) at depths 〉 200 m. We found nutrient-like profiles of Fe in the Atlantic-influenced Nansen basin, surface enrichment in the surface over the Amundsen and Makarov basins and scavenging effects in the deep Makarov basin. A highly detailed surface transect consisting of two sections crossing the surface flow from the Siberian continental shelf to the Fram Strait, the TransPolar Drift (TPD), clearly indicates the flow path of the riverine contribution to Fe and Fe-binding organic ligands with concentrations of 0.7 to 4.4 nM and 1.6 to 4.1 Eq. nM Fe, respectively. This is on average 4.5 times higher in DFe and 1.7 times higher in Fe-binding organic ligands than outside the TPD flow path. Conditional binding strengths of ligands in the entire dataset were remarkably similar at 11.45 ≤ LogK′ ≤ 12.63. Increased organic Fe-binding organic ligand concentrations were evident in the Arctic Ocean surface. To better identify the organic substances responsible for Fe complexation in the Arctic Ocean, diverse analytical approaches and a standard other than Suwannee River Fulvic Acid are recommended.
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  • 34
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    The effects of hypoxia on active ionic transport processes in the gill epithelium of hyperregulating crab, Carcinus maneas (2017)
    Elsevier
    In:  EPIC3Comparative Biochemistry and Physiology, Part A, Elsevier, 211, pp. 61-68
    Details
    Publication Date: 2018-02-05
    Description: Effects of hypoxia on the osmorespiratory functions of the posterior gills of the shore crab Carcinus maenas acclimated to 12 ppt seawater (DSW) were studied. Short-circuit current (Isc) across the hemilamella (one epithelium layer supported by cuticle) was substantially reduced under exposure to 1.6, 2.0, or 2.5 mg O2/L hypoxic saline (both sides of epithelium) and fully recovered after reoxygenation. Isc was reduced equally in the epithelium exposed to 1.6 mg O2/L on both sides and when the apical side was oxygenated and the basolateral side solely exposed to hypoxia. Under 1.6 mg O2/L, at the level of maximum inhibition of Isc, conductance was decreased from 40.0 mS cm−2 to 34.7 mS cm−2 and fully recovered after reoxygenation. Isc inhibition under hypoxia and reduced 86Rb+ (K+) fluxes across apically located K+ channels were caused preferentially by reversible inhibition of basolaterally located and ouabain sensitive Na+,K+-ATPase mediated electrogenic transport. Reversible inhibition of Isc is discussed as decline in active transport energy supply down regulating metabolic processes and saving energy during oxygen deprivation. In response to a 4 day exposure of Carcinus to 2.0 mg O2/L, hemolymph Na+ and Cl− concentration decreased, i.e. hyperosmoregulation was weakened. Variations of the oxygen concentration level and exposure time to hypoxia lead to an increase of the surface of mitochondria per epithelium area and might in part compensate for the decrease in oxygen availability under hypoxic conditions.
    Repository Name: EPIC Alfred Wegener Institut
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  • 35
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    Using the FlowCam to Validate an Enzymatic Digestion Protocol Applied to Assess the Occurrence of Microplastics in the Southern North Sea (2017)
    Elsevier
    In:  EPIC3Fate and Impact of Microplastics in Marine Ecosystems, MICRO 2016: Fate and Impact of Microplastics in Marine Ecosystems, Elsevier, pp. 92-93
    Details
    Publication Date: 2018-02-11
    Description: As the plastic production has been rising since the last five decades, so does the concern for the occurrence of microplastic particles (〈5 mm)in the marine environment during the past years. But still by now the extent of this microplastic pollution of coastal waters and the open ocean remains unclear. Since monitoring the abundance of microplastics in the marine environment is requested by the Marine Strategy Framework Directive (MSFD) standardized and reliable methods forthe detection of microplastics are urgently needed. Studies differ mainly in their purification methods, aiming to reduce biogenic material in environmental samples without altering the plastic polymers to facilitate a clear assignment of the microplastics. In the present and ongoing study the purification method consists of a treatment with technical enzymes and detergents to reduce the use of oxidants and avoid the use of strong acids as well as the subsequent identification and quantification of microplastics applying Focal Plane Array (FPA)-based μFourier Transform Infrared (μFT-IR) spectroscopy.
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  • 36
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    Growth, toxin production, active oxygen species and catalase activity of Microcystis aeruginosa (Cyanophyceae) exposed to temperature stress (2016)
    Elsevier
    In:  EPIC3Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology, Elsevier, 189, pp. 22-30, ISSN: 1532-0456
    Details
    Publication Date: 2019-07-17
    Description: Microcystis are known for their potential ability to synthesize toxins, mainly microcystins (MCs). In order to evaluate the effects of temperature on chlorophyll a (Chl a), growth, physiological responses and toxin production of a native Microcystis aeruginosa, we exposed the cells to low (23 °C) and high (29 °C) temperature in addition to a 26 °C control treatment. Exponential growth rate was significantly higher at 29 °C compared to 23 °C and control, reaching 0.43, 0.32 and 0.33 day−1 respectively. In addition, there was a delay of the start of exponential growth at 23 °C. However, the intracellular concentration of Chl a decreased significantly due to temperature change. A significant increase in intracellular ROS was observed in coincidence with the activation of enzymatic antioxidant catalase (CAT) during the first two days of exposure to 23° and 29 °C in comparison to the control experiment, decreasing thereafter to nearly initial values. Five MCs were determined by LC-MS/MS analysis. In the experiments, the highest MC concentration, 205 fg [Leu1] MC-LR.cell− 1 expressed as MC-LR equivalent was measured in the beginning of the experiment and subsequently declined to 160 fg.cell− 1 on day 2 and 70 fg.cell− 1 on day 4 in cells exposed to 29 °C. The same trend was observed for all other MCs except for the least abundant MC-LR which showed a continuous increase during exposure time. Our results suggest a high ability of M. aeruginosa to perceive ROS and to rapidly initiate antioxidant defenses with a differential response on MC production.
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  • 37
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    Dangerous hitchhikers? Evidence for potentially pathogenic Vibrio spp. on microplastic particles (2016)
    Elsevier
    In:  EPIC3Marine Environmental Research, Elsevier, 120, pp. 1-8, ISSN: 01411136
    Details
    Publication Date: 2016-10-01
    Repository Name: EPIC Alfred Wegener Institut
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  • 38
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    Presence of rapidly degrading permafrost plateaus in south-central Alaska (2016)
    Copernicus
    In:  EPIC3The Cryosphere, Copernicus, 10(6), pp. 2673-2692, ISSN: 1994-0424
    Details
    Publication Date: 2016-11-16
    Description: Permafrost presence is determined by a complex interaction of climatic, topographic, and ecological conditions operating over long time scales. In particular, vegetation and organic layer characteristics may act to protect permafrost in regions with a mean annual air temperature (MAAT) above 0°C. In this study, we document the presence of residual permafrost plateaus in the western Kenai Peninsula lowlands of south-central Alaska, a region with a MAAT of 1.5+/-1 °C (1981–2010). Continuous ground temperature measurements between 16 September 2012 and 15 September 2015, using calibrated thermistor strings, documented the presence of warm permafrost (-0.04 to -0.08 °C). Field measurements (probing) on several plateau features during the fall of 2015 showed that the depth to the permafrost table averaged 1.48m but at some locations was as shallow as 0.53 m. Late winter surveys (augering, coring, and GPR) in 2016 showed that the average seasonally frozen ground thickness was 0.45 m, overlying a talik above the permafrost table. Measured permafrost thickness ranged from 0.33 to 〉6.90 m. Manual interpretation of historic aerial photography acquired in 1950 indicates that residual permafrost plateaus covered 920 ha as mapped across portions of four wetland complexes encompassing 4810 ha. However, between 1950 and ca. 2010, permafrost plateau extent decreased by 60.0 %, with lateral feature degradation accounting for 85.0% of the reduction in area. Permafrost loss on the Kenai Peninsula is likely associated with a warming climate, wildfires that remove the protective forest and organic layer cover, groundwater flow at depth, and lateral heat transfer from wetland surface waters in the summer. Better understanding the resilience and vulnerability of ecosystem-protected permafrost is critical for mapping and predicting future permafrost extent and degradation across all permafrost regions that are currently warming. Further work should focus on reconstructing permafrost history in south-central Alaska as well as additional contemporary observations of these ecosystem-protected permafrost sites south of the regions with relatively stable permafrost.
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  • 39
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    Defining the Baselines and Standards for Microplastics Analyses in European Waters (JPI-O BASEMAN) (2016)
    Elsevier
    In:  EPIC3MICRO 2016. Fate and Impact of Microplastics in Marine Ecosystems, MICRO 2016. Fate and Impact of Microplastics in Marine Ecosystems, Elsevier, 1 p., pp. 120-120, ISBN: 9780128122716
    Details
    Publication Date: 2016-12-12
    Repository Name: EPIC Alfred Wegener Institut
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  • 40
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    Breaking Down the Plastic Age (2017)
    Elsevier
    In:  EPIC3Fate and Impact of Microplastics in Marine Ecosystems, MICRO 2016, Amsterdam, Elsevier, pp. 177-181
    Details
    Publication Date: 2017-04-25
    Repository Name: EPIC Alfred Wegener Institut
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  • 41
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    Ice core record of dust sources in the western United States over the last 300 years (2016)
    Elsevier
    In:  EPIC3Chemical Geology, Elsevier, 442, pp. 160-173, ISSN: 00092541
    Details
    Publication Date: 2017-06-07
    Description: Over the past ~ 5000 years, amplified dust generation and deposition in the American West has been linked to human activity. In recent decades, intensified rates of agriculture and livestock grazing have been correlated with greater dust production detected on seasonal to annual timescales. The combination of land use intensification and climate change (i.e. increased drought frequency) in North America highlights the importance of characterizing the sources of dust both before and after the influence of anthropogenic activity. We apply high-precision geochemical and isotopic (Sr and Nd isotopes) techniques to an ice core from the Upper Fremont Glacier (Wyoming, USA) to produce the first glacial dataset from the American West. Our Sr-Nd isotopic composition data indicates the evolving dust provenance to the Upper Fremont Glacier (UFG) from a long-range transport of mineral dust to a local source. This increasing input of dust from a local source is supported by a rise in average dust particle diameter combined with greater average dust concentration throughout the record. The greater presence of dust particles smaller than 2.5 μm in the most recent samples from UFG ice core record support existing satellite and sediment core data regarding the effects of anthropogenic activity upon dust sources and pathways in the American West. Although the Sr-Nd isotope database in North America needs be expanded, our results provide a survey of windborne dust through the past 270 years.
    Repository Name: EPIC Alfred Wegener Institut
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  • 42
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    The structural elements and tectonics of the Lake Van basin (Eastern Anatolia) from multi-channel seismic reflection profiles (2017)
    Elsevier
    In:  EPIC3Journal of African Earth Sciences, Elsevier, 129, pp. 165-178
    Details
    Publication Date: 2017-06-16
    Description: This study analyzed multi-channel seismic reflection data from Lake Van, Eastern Anatolia, to provide key information on the structural elements, deformational patterns and overall tectonic structure of the Lake Van basin. The seismic data reveal three subbasins (the Tatvan, northern and Ahlat subbasins) separated by structural ridges (the northern and Ahlat ridges). The Tatvan basin is a tilted wedge-block in the west, it is a relatively undeformed and flat-lying deep basin, forming a typical example of strike-slip sedimentation. Seismic sections reveal that the deeper sedimentary sections of the Tatvan basin are locally folded, gently in the south and more intensely further north, suggesting a probable gravitational “wedge-block” instability, oblique to the northern margin. The northern subbasin, bounded by normal oblique faults, forms a basin-margin graben structure that is elongated in a northeast-southwest direction. The east-west trending Ahlat ridge forms a fault-wedged sedimentary ridge and appears to offset by reverse oblique faults forming as a push-up rhomb horst structure. The Ahlat subbasin is a fault-wedged trough fill that is elongated in the west-east direction and appears as a horst-foot graben formed by the normal oblique faults. The northeast-southwest directed northern ridge is a faulted crestal terrace of a sublacustrine basement block. Its step-like morphology, in response to the downfaulting of the Tatvan basin, as well as its backthrusted appearance, indicates the normal oblique nature of the bounding faults. The lacustrine shelf and slope show distinctive stratigraphic features; progradational deltas, submerged fluvial channels, distorted and collapsed beddings and soft sediment deformation structures, characterizing a highly unstable nature of shelf caused by strong oblique faulting and related earthquakes. The faulting caused uplift of the Çarpanak spur zone, together with the northeastern Erek delta, deformation of deltaic structures and subsequently exposing the shelf and slope areas. The exposed areas are evident in the angular unconformity surface of the Çarpanak basement block with the northeastern Erek delta and thinned sediments. The uplift resulted in the asymmetric depositional emplacement of the southeastern delta that is controlled by a series of ramp anticlines/low angle reverse faults. The Deveboynu subbasin and Varis spur zone form wide fault-controlled depressions with thick sediments that are elongated in the north-south direction. These subbasins appear as a small pull-apart boundary formed by normal oblique faults at the western end of the southeastern delta.
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  • 43
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    Geochemistry and volatile content of magmas feeding explosive eruptions at Telica volcano (Nicaragua) (2017)
    Elsevier
    Details
    Publication Date: 2017-09-11
    Description: Telica volcano, in north-west Nicaragua, is a young stratovolcano of intermediate magma composition producing frequent Vulcanian to phreatic explosive eruptions. The Telica stratigraphic record also includes examples of (pre)historic sub-Plinian activity. To refine our knowledge of this very active volcano, weanalyzedmajor element composition and volatile content of melt inclusions fromsomestratigraphically significant Telica tephra deposits. These include: (1) the Scoria Telica Superior (STS) deposit (2000 to 200 years Before Present; Volcanic Explosive Index, VEI, of 2–3) and (2) pyroclasts from the post-1970s eruptive cycle (1982; 2011). Based on measurements with nanoscale secondary ion mass spectrometry, olivine-hosted (forsterite [Fo] N 80) glass inclusions fall into 2 distinct clusters: a group of H2O-rich (1.8–5.2 wt%) inclusions, similar to those of nearby Cerro Negro volcano, and a second group of CO2-rich (360–1700 μg/g CO2) inclusions (Nejapa, Granada). Model calculations show that CO2 dominates the equilibrium magmatic vapor phase in the majority of the primitive inclusions (XCO2 N 0.62–0.95). CO2, sulfur (generally b2000 μg/g) and H2O are lost to the vapor phase during deep decompression (P N 400 MPa) and early crystallization of magmas. Chlorine exhibits a wide concentration range (400–2300 μg/g) in primitive olivine-entrapped melts (likely suggesting variable source heterogeneity) and is typically enriched in the most differentiated melts (1000–3000 μg/g). Primitive, volatile-rich olivine-hosted melt inclusions (entrapment pressures, 5–15 km depth) are exclusively found in the largest-scale Telica eruptions (exemplified by STS in our study). These eruptions are thus tentatively explained as due to injection of deep CO2-rich mafic magma into the shallow crustal plumbing system. More recent (post-1970), milder (VEI 1–2) eruptions, instead, do only exhibit evidence for low-pressure (P b 50–60 MPa), volatile-poor (H2O b 0.3–1.7 wt%; CO2 b 23–308 μg/g) magmatic conditions. These are manifested as andesitic magmas, recording multiple magma mixing events, in pyroxene inclusions.Wepropose that post-1970s eruptions are possibly related to the high viscosity of resident magma in shallow plumbing system (b2.4 km), due to crystallization and degassing
    Description: Published
    Description: 131-148
    Description: 1V. Storia eruttiva
    Description: JCR Journal
    Keywords: Telica, Nicaragua ; 04.08. Volcanology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 44
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    Origin of primitive ultra-calcic arc melts at crustal conditions -Experimental evidence on the La Sommata basalt, Vulcano, Aeolian Islands. (2017)
    Elsevier
    Details
    Publication Date: 2017-09-11
    Description: characterization of ultra-calcic arc melts, equilibrium phase relations have been determined experimentally for the La Sommata basalt (Som-1, Vulcano, Aeolian arc). Som-1 (Na2O + K2O = 4.46 wt.%, CaO = 12.97 wt.%, MgO = 8.78 wt.%, CaO/Al2O3 = 1.03) is a reference primitive ne-normative arc basalt with a strong ultra-calcic affinity. The experiments have been performed between 44 and 154 MPa, 1050 and 1150 °C and from NNO + 0.2 to NNO + 1.9. Fluid-present conditions were imposed with H2O–CO2 mixtures yielding melt H2O concentrations from0.7 to 3.5wt.%. Phases encountered include clinopyroxene, olivine, plagioclase and Fe-oxide. Clinopyroxene is slightly earlier than olivine in the crystallization sequence. It is the liquidus phase at 150 MPa, being joined by olivine on the liquidus between 44 and 88MPa. Plagioclase is the third phase to appear in the crystallization sequence and orthopyroxene was not found. Experimental clinopyroxenes (Fs7–16) and olivines (Fo78–92) partially reproduce the natural phenocryst compositions (respectively Fs5–7 and Fo87–91). Upon progressive crystallization, experimental liquids shift towards higher SiO2 (up to ~55 wt.%), Al2O3 (up to ~18 wt.%) and K2O (up to ~5.5wt.%) and lower CaO,MgO and CaO/Al2O3. Experimental glasses and natural whole-rock compositions overlap, indicating that progressive crystallization of Som-1 type melts can generate differentiated compositions such as those encountered at Vulcano. The lowpressure cotectic experimental glasses reproduce glass inclusions in La Sommata clinopyroxene but contrast with glass inclusions in olivine which preserve basaltic melts more primitive than Som-1. Phase relations for the La Sommata basalt are identical in all critical aspects to those obtained previously on a synthetic ultra-calcic arc composition. In particular, clinopyroxene+olivine co-saturation occurs at very low pressures (≤100 MPa). Ultra-calcic arc compositions do not represent primary mantle melts but result from the interaction between a primary mantle melt and clinopyroxene-bearing rocks in the arc crust. At Vulcano, primitive ultra-calcic end-member melts were generated between 250 and 350 MPa in the lower magma accumulation zone by reaction between hot primitive melts and wehrlitic or gabbroic lithologies. At Stromboli, golden pumices and glass inclusions with an ultra-calcic affinity were also generated at shallow pressures, between 150 and 250 MPa, suggesting that the interaction model is of general significance in the Aeolian arc.
    Description: Published
    Description: 85-101
    Description: 2V. Struttura e sistema di alimentazione dei vulcani
    Description: JCR Journal
    Keywords: Primitive arc magmas, Ultra-calcic Experiments, Phase equilibria, Vulcano, Aeolian arc ; Petrology
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  • 45
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    Dissolved Carbon in Groundwater versus Gas Emissions from the Soil: The Two Sides of the Same Coin (2017)
    Elsevier
    Details
    Publication Date: 2017-12-13
    Description: This study focuses on the interaction among deep volcanic/hydrothermal gases, groundwater and soil gases at Vulcano Island (Aeolian Archipelago, Italy). The chemical-physical parameters of the groundwater, the total dissolved inorganic carbon (TDIC) and the isotopic composition of the CO2 dissolved in groundwater are reported and discussed. Furthermore, a comparison between soil gases and groundwater indicates that groundwater and soil gases show the same qualitative information, giving a good overall picture of the main degassing zones of a volcanic system, whereas the soil gas discharge provides an evaluation of the mass released by the deep feeding system. This approach can be a useful tool both to characterize mixing and/or interaction processes among different sources and for a monitoring of degassing activity of a volcanic system.
    Description: Published
    Description: 116-119
    Description: 2V. Struttura e sistema di alimentazione dei vulcani
    Description: 4V. Dinamica dei processi pre-eruttivi
    Description: N/A or not JCR
    Keywords: Soil CO2 flux ; Dissolved gases ; Isotope composition of CO2 ; Groundwaters ; Vulcano Island ; 03.02. Hydrology ; 04.08. Volcanology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 46
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    Determination of the stable iron isotopic composition of sequentially leached iron phases in marine sediments (2016)
    Elsevier
    In:  EPIC3Chemical Geology, Elsevier, 421, pp. 93-102
    Details
    Publication Date: 2019-07-17
    Description: Reactive iron (oxyhydr)oxide minerals preferentially undergo early diagenetic redox cycling which can result in the production of dissolved Fe(II), the adsorption of Fe(II) onto particle surfaces, and the formation of authigenic Fe minerals. The partitioning of iron in sediments has traditionally been studied by applying sequential extractions that target operationally-defined iron phases. Here, we complement an existing sequential leaching method by developing a sample processing protocol for δ56Fe analysis, which we subsequently use to study Fe phase-specific fractionation related to dissimilatory iron reduction in a modern marine sediment. Carbonate-Fe was extracted by acetate, easily reducible oxides (e.g. ferrihydrite and lepidocrocite) by hydroxylamine–HCl, reducible oxides (e.g. goethite and hematite) by dithionite–citrate, and magnetite by ammonium oxalate. Subsequently, the samples were repeatedly oxidized, heated and purified via Fe precipitation and column chromatography. The method was applied to surface sediments collected from the North Sea, south of the island of Helgoland. The acetate-soluble fraction (targeting siderite and ankerite) showed a pronounced downcore δ56Fe trend. This iron pool was most depleted in 56Fe close to the sediment–water interface, similar to trends observed for pore-water Fe(II). We interpret this pool as surface-reduced Fe(II), rather than siderite or ankerite, that was open to electron and atom exchange with the oxide surface. Common extractions using 0.5 M HCl or Na-dithionite alone may not resolve such trends, as they dissolve iron from isotopically distinct pools leading to a mixed signal. Na-dithionite leaching alone, for example, targets the sum of reducible Fe oxides that potentially differ in their isotopic fingerprint. Hence, the development of a sequential extraction Fe isotope protocol provides a new opportunity for detailed study of the behavior of iron in a wide range of environmental settings.
    Repository Name: EPIC Alfred Wegener Institut
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  • 47
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    Satellite-derived changes in the permafrost landscape of central Yakutia, 2000–2011: Wetting, drying, and fires (2016)
    Elsevier
    In:  EPIC3Global and Planetary Change, Elsevier, 139, pp. 116-127, ISSN: 09218181
    Details
    Publication Date: 2016-02-12
    Description: The focus of this research has been on detecting changes in lake areas, vegetation, land surface temperatures, and the area covered by snow, using data from remote sensing. The study area covers the main (central) part of the Lena River catchment in the Yakutia region of Siberia (Russia), extending from east of Yakutsk to the central Siberian Plateau, and from the southern Lena River to north of the Vilyui River. Approximately 90% of the area is underlain by continuous permafrost. Remote sensing products were used to analyze changes in water bodies, land surface temperature (LST), and leaf area index (LAI), as well as the occurrence and extent of forest fires, and the area and duration of snow cover. The remote sensing analyses (for LST, snow cover, LAI, and fire) were based on MODIS–derived NASA products (250–1000 m) for 2000 to 2011. Changes in water bodies were calculated from two mosaics of (USGS) Landsat (30 m) satellite images from 2002 and 2009. Within the study area's 315,000 km2 the total area covered by lakes increased by 17.9% between 2002 and 2009, but this increase varied in different parts of the study area, ranging between 11% and 42%. The land surface temperatures showed a consistent warming trend, with an average increase of about 0.12 °C/year. The average rate of warming during the April–May transition period was 0.17 °C/year and 0.19 °C/year in the September–October period, but ranged up to 0.49 °C/year during September–October. Regional differences in the rates of land surface temperature change, and possible reasons for the temperature changes, are discussed with respect to changes in the land cover. Our analysis of a broad spectrum of variables over the study area suggests that the spring warming trend is very likely to be due to changes in the area covered by snow. The warming trend observed in fall does not, however, appear to be directly related to any changes in the area of snow cover, or to the atmospheric conditions, or to the proportion of the land surface that is covered by water (i.e., to wetting and drying). Supplementary data (original data, digitized version of the maps, metadata) are archived under PANGAEA (http://dx.doi.org/10.1594/PANGAEA.855124).
    Repository Name: EPIC Alfred Wegener Institut
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  • 48
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    Presence of rapidly degrading permafrost plateaus in southcentral Alaska (2016)
    Copernicus
    In:  EPIC3The Cryosphere Discussions, Copernicus
    Details
    Publication Date: 2016-05-26
    Description: Permafrost presence is determined by a complex interaction of climatic, topographic, and ecological conditions operating over long time scales. In particular, vegetation and organic layer characteristics may act to protect permafrost in regions with a mean annual air temperature (MAAT) above 0 °C. In this study, we document the presence of residual permafrost plateaus on the western Kenai Peninsula lowlands of southcentral Alaska, a region with a MAAT of 1.5 ± 1 °C (1981 to 2010). Continuous ground temperature measurements between 16 September 2012 and 15 September 2015, using calibrated thermistor strings, documented the presence of warm permafrost (−0.04 to −0.08 °C). Field measurements (probing) on several plateau features during the fall of 2015 showed that the depth to the permafrost table averaged 1.48 m but was as shallow as 0.53 m. Late winter surveys (drilling, coring, and GPR) in 2016 showed that the average seasonally frozen ground thickness was 0.45 m, overlying a talik above the permafrost table. Measured permafrost thickness ranged from 0.33 to 〉 6.90 m. Manual interpretation of historic aerial photography acquired in 1950 indicates that residual permafrost plateaus covered 920 ha as mapped across portions of four wetland complexes encompassing 4810 ha. However, between 1950 and ca. 2010, permafrost plateau extent decreased by 60 %, with lateral feature degradation accounting for 85 % of the reduction in area. Permafrost loss on the Kenai Peninsula is likely associated with a warming climate, wildfires that remove the protective forest and organic layer cover, groundwater flow at depth, and lateral heat transfer from wetland surface waters in the summer. Better understanding the resilience and vulnerability of ecosystem-protected permafrost is critical for mapping and predicting future permafrost extent and degradation across all permafrost regions that are currently warming. Further work should focus on reconstructing permafrost history in southcentral Alaska as well as additional contemporary observations of these ecosystem-protected permafrost sites lying south of the regions with relatively stable permafrost.
    Repository Name: EPIC Alfred Wegener Institut
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  • 49
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    Southern Ocean phytoplankton physiology in a changing climate (2016)
    Elsevier
    In:  EPIC3Journal of Plant Physiology, Elsevier
    Details
    Publication Date: 2016-06-23
    Description: The Southern Ocean (SO) is a major sink for anthropogenic atmospheric carbon dioxide (CO2), potentially harbouring even greater potential for additional sequestration of CO2 through enhanced phytoplankton productivity. In the SO, primary productivity is primarily driven by bottom up processes (physical and chemical conditions) which are spatially and temporally heterogeneous. Due to a paucity of trace metals (such as iron) and high variability in light, much of the SO is characterised by an ecological paradox of high macronutrient concentrations yet uncharacteristically low chlorophyll concentrations. It is expected that with increased anthropogenic CO2 emissions and the coincident warming, the major physical and chemical process that govern the SO will alter, influencing the biological capacity and functioning of the ecosystem. This review focuses on the SO primary producers and the bottom up processes that underpin their health and productivity. It looks at the major physico-chemical drivers of change in the SO, and based on current physiological knowledge, explores how these changes will likely manifest in phytoplankton, specifically, what are the physiological changes and floristic shifts that are likely to ensue and how this may translate into changes in the carbon sink capacity, net primary productivity and functionality of the SO.
    Repository Name: EPIC Alfred Wegener Institut
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  • 50
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    Advection in polar and sub-polar environments: Impacts on high latitude marine ecosystems (2016)
    Elsevier
    In:  EPIC3Progress in Oceanography, Elsevier, 149, pp. 40-81
    Details
    Publication Date: 2017-06-14
    Description: We compare and contrast the ecological impacts of atmospheric and oceanic circulation patterns on polar and sub-polar marine ecosystems. Circulation patterns differ strikingly between the north and south. Meridional circulation in the north provides connections between the sub-Arctic and Arctic despite the presence of encircling continental landmasses, whereas annular circulation patterns in the south tend to isolate Antarctic surface waters from those in the north. These differences influence fundamental aspects of the polar ecosystems from the amount, thickness and duration of sea ice, to the types of organisms, and the ecology of zooplankton, fish, seabirds and marine mammals. Meridional flows in both the North Pacific and the North Atlantic oceans transport heat, nutrients, and plankton northward into the Chukchi Sea, the Barents Sea, and the seas off the west coast of Greenland. In the North Atlantic, the advected heat warms the waters of the southern Barents Sea and, with advected nutrients and plankton, supports immense biomasses of fish, seabirds and marine mammals. On the Pacific side of the Arctic, cold waters flowing northward across the northern Bering and Chukchi seas during winter and spring limit the ability of boreal fish species to take advantage of high seasonal production there. Southward flow of cold Arctic waters into sub-Arctic regions of the North Atlantic occurs mainly through Fram Strait with less through the Barents Sea and the Canadian Archipelago. In the Pacific, the transport of Arctic waters and plankton southward through Bering Strait is minimal. In the Southern Ocean, the Antarctic Circumpolar Current and its associated fronts are barriers to the southward dispersal of plankton and pelagic fishes from sub-Antarctic waters, with the consequent evolution of Antarctic zooplankton and fish species largely occurring in isolation from those to the north. The Antarctic Circumpolar Current also disperses biota throughout the Southern Ocean, and as a result, the biota tends to be similar within a given broad latitudinal band. South of the Southern Boundary of the ACC, there is a large-scale divergence that brings nutrient-rich water to the surface. This divergence, along with more localized upwelling regions and deep vertical convection in winter, generates elevated nutrient levels throughout the Antarctic at the end of austral winter. However, such elevated nutrient levels do not support elevated phytoplankton productivity through the entire Southern Ocean, as iron concentrations are rapidly removed to limiting levels by spring blooms in deep waters. However, coastal regions, with the upward mixing of iron, maintain greatly enhanced rates of production, especially in coastal polynyas. In these coastal areas, elevated primary production supports large biomasses of zooplankton, fish, seabirds, and mammals. As climate warming affects these advective processes and their heat content, there will likely be major changes in the distribution and abundance of polar biota, in particular the biota dependent on sea ice.
    Repository Name: EPIC Alfred Wegener Institut
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    Lessons learned from applying a forest gap model to understand ecosystem and carbon dynamics of complex tropical forests (2016)
    Elsevier
    In:  EPIC3Ecological Modelling, Elsevier, 326, pp. 124-133, ISSN: 03043800
    Details
    Publication Date: 2016-03-17
    Description: Forests worldwide are threatened by various environmental and anthropogenic hazards, especially tropical forests. Knowledge on the impacts of these hazards on forest structure and dynamics has been compiled in empirical studies. However, the results of these studies are often not sufficient for long-term projections and extrapolations to large spatial scales especially for unprecedented environmental conditions, which require both the identification and understanding of key underlying processes. Forest models bridge this gap by incorporating multiple ecological processes in a dynamic framework (i.e. including a realistic model structure) and addressing the complexity of forest ecosystems. Here, we describe the evolution of the individual-based and process-based forest gap model FORMIND and its application to tropical forests. At its core, the model includes physiological processes on tree level (photosynthesis, respiration, tree growth, mortality, regeneration, competition). During the past two decades, FORMIND has been used to address various scientific questions arising from different forest types by continuously extending the model structure. The model applications thus provided understanding in three main aspects: (1) the grouping of single tree species into plant functional types is a successful approach to reduce complexity in vegetation models, (2) structural realism was necessary to analyze impacts of natural and anthropogenic disturbances such as logging, fragmentation, or drought, and (3) complex ecological processes such as carbon fluxes in tropical forests – starting from the individual tree level up to the entire forest ecosystem – can be explored as a function of forest structure, species composition and disturbance regime. Overall, this review shows how the evolution of long-term modelling projects not only provides scientific understanding of forest ecosystems, but also provides benefits for ecological theory and empirical study design.
    Repository Name: EPIC Alfred Wegener Institut
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    The impact of glacier retreat from the Ross Sea on local climate: Characterization of mineral dust in the Taylor Dome ice core, EastAntarctica (2016)
    Elsevier
    In:  EPIC3Earth and Planetary Science Letters, Elsevier, 444, pp. 34-44
    Details
    Publication Date: 2016-05-02
    Description: Recent declines in ice shelf and sea ice extent experienced in polar regions highlight the importance of evaluating variations in local weather patterns in response to climate change. Airborne mineral particles (dust) transported through the atmosphere and deposited on ice sheets and glaciers in Antarctica and Greenland can provide a robust set of tools for resolving the evolution of climatic systems through time. Here we present the first high time resolution radiogenic isotope (strontium and neodymium) data for Holocene dust in a coastal East Antarctic ice core, accompanied by rare earth element composition, dust concentration, and particle size distribution during the last deglaciation. We aim to use these combined ice core data to determine dust provenance, with variations indicative of shifts in either dust production, sources, and/or transport pathways. We analyzed a series of 17 samples from the Taylor Dome (77◦47'47''S, 158◦43'26''E) ice core, 113–391m in depth from 1.1–31.4ka. Radiogenic isotopic and rare earth element compositions of dust during the last glacial period are in good agreement with previously measured East Antarctic ice core dust records. In contrast, the Holocene dust dataset displays a broad range in isotopic and rare earth element compositions, suggesting a shift from long-range transported dust to a more variable, local input that may be linked to the retreat of the Ross Ice Shelf during the last deglaciation. Observed changes in the dust cycle inferred from a coastal East Antarctic ice core can thus be used to infer an evolving local climate.
    Repository Name: EPIC Alfred Wegener Institut
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  • 53
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    Estimation of high-resolution terrestrial evapotranspiration from Landsat data using a simple Taylor skill fusion method (2017)
    Elsevier
    In:  EPIC3Journal of Hydrology, Elsevier, 553, pp. 508-526, ISSN: 00221694
    Details
    Publication Date: 2021-08-16
    Description: Estimation of high-resolution terrestrial evapotranspiration (ET) from Landsat data is important in many climatic, hydrologic, and agricultural applications, as it can help bridging the gap between existing coarse-resolution ET products and point-based field measurements. However, there is large uncertainty among existing ET products from Landsat that limit their application. This study presents a simple Taylor skill fusion (STS) method that merges five Landsat-based ET products and directly measured ET from eddy covariance (EC) to improve the global estimation of terrestrial ET. The STS method uses a weighted average of the individual ET products and weights are determined by their Taylor skill scores (S). The validation with site-scale measurements at 206 EC flux towers showed large differences and uncertainties among the five ET products. The merged ET product exhibited the best performance with a decrease in the averaged root-mean-square error (RMSE) by 2–5 W/m2 when compared to the individual products. To evaluate the reliability of the STS method at the regional scale, the weights of the STS method for these five ET products were determined using EC ground-measurements. An example of regional ET mapping demonstrates that the STS-merged ET can effectively integrate the individual Landsat ET products. Our proposed method provides an improved high-resolution ET product for identifying agricultural crop water consumption and providing a diagnostic assessment for global land surface models.
    Repository Name: EPIC Alfred Wegener Institut
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  • 54
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    Surface and bottom temperature and salinity climatology along the continental shelf off the Canadian and U.S. East Coasts (2016)
    Elsevier
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Continental Shelf Research 124 (2016): 165-181, doi:10.1016/j.csr.2016.06.005.
    Description: A new hydrographic climatology has been created for the continental shelf region, extending from the Labrador shelf to the Mid-Atlantic Bight. The 0.2-degree climatology combines all available observations of surface and bottom temperature and salinity collected between 1950 and 2010 along with the location, depth and date of these measurements. While climatological studies of surface and bottom temperature and salinity have been presented previously for various regions along the Canadian and U.S. shelves, studies also suggest that all these regions are part of one coherent system. This study focuses on the coherent structure of the mean seasonal cycle of surface and bottom temperature and salinity and its variation along the shelf and upper slope. The seasonal cycle of surface temperature is mainly driven by the surface heat flux and exhibits strong dependency on latitude (r≈−0.9). The amplitude of the seasonal cycle of bottom temperature is rather dependent on the depth, while the spatial distribution of bottom temperature is correlated with latitude. The seasonal cycle of surface salinity is influenced by several components, such as sea-ice on the northern shelves and river discharge in the Gulf of St. Lawrence. The bottom salinity exhibits no clear seasonal cycle, but its spatial distribution is highly correlated with bathymetry, thus Slope Water and its intrusion on the shelf can be identified by its relatively high salinity compared to shallow, fresher shelf water. Two different regimes can be identified, especially on the shelf, separated by the Laurentian Channel: advection influences the phasing of the seasonal cycle of surface salinity and bottom temperature to the north, while in the southern region, river runoff and air-sea heat flux forcing are dominant, especially over the shallower bathymetry.
    Description: Support from NSF OCE PO to Y-OK (OCE-1242989 and OCE-1435602) and SJL (OCE-1332666).
    Keywords: Seasonal climatology ; Temperature ; Salinity ; Dataset ; Shelf
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    Phosphorus dynamics in biogeochemically distinct regions of the southeast subtropical Pacific Ocean (2017)
    Elsevier
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Progress in Oceanography 151 (2017): 261–274, doi:10.1016/j.pocean.2016.12.007.
    Description: The southeast subtropical Pacific Ocean was sampled along a zonal transect between the coasts of Chile and Easter Island. This remote area of the world’s ocean presents strong gradients in physical (e.g., temperature, density and light), chemical (e.g., salinity and nutrient concentrations) and microbiological (e.g., cell abundances, biomass and specific growth rates) properties. The goal of this study was to describe the phosphorus (P) dynamics in three main ecosystems along this transect: the upwelling regime off the northern Chilean coast, the oligotrophic area associated with the southeast subtropical Pacific gyre and the transitional area in between these two biomes. We found that inorganic phosphate (Pi) concentrations were high and turnover times were long (〉210 nmol l−1 and 〉31 d, respectively) in the upper water column, along the entire transect. Pi uptake rates in the gyre were low (euphotic layer integrated rates were 0.26 mmol m−2 d−1 in the gyre and 1.28 mmol m−2 d−1 in the upwelling region), yet not only driven by decreases in particle mass or cell abundance (particulate P- and cell- normalized Pi uptake rates in the euphotic layer were ∼1–4 times and ∼3–15 times lower in the gyre than in the upwelling, respectively). However these Pi uptake rates were at or near the maximum Pi uptake velocity (i.e., uptake rates in Pi amended samples were not significantly different from those at ambient concentration: 1.5 and 23.7 nmol l−1 d−1 at 50% PAR in the gyre and upwelling, respectively). Despite the apparent Pi replete conditions, selected dissolved organic P (DOP) compounds were readily hydrolyzed. Nucleotides were the most bioavailable of the DOP substrates tested. Microbes actively assimilated adenosine-5′-triphosphate (ATP) leading to Pi and adenosine incorporation as well as Pi release to the environment. The southeast subtropical Pacific Ocean is a Pi-sufficient environment, yet DOP hydrolytic processes are maintained and contribute to P-cycling across the wide range of environmental conditions present in this ecosystem.
    Description: Funds for this work were provided by the Gordon and Betty Moore Foundation’s Marine Microbiology Initiative (D.M.K., 3794) and the Center for Microbial Oceanography: Research and Education (C-MORE, National Science Foundation, D.M.K., EF0424599).
    Keywords: Phosphorus dynamics ; Microbes ; Stocks ; Fluxes ; Southeast subtropical Pacific Ocean
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    Neodymium isotopes and concentrations in aragonitic scleractinian cold-water coral skeletons - modern calibration and evaluation of palaeo-applications (2017)
    Elsevier
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Chemical Geology 453 (2017): 146–168, doi:10.1016/j.chemgeo.2017.01.022.
    Description: Cold-water corals (CWCs) are unique archives of mid-depth ocean chemistry and have been used successfully to reconstruct the neodymium (Nd) isotopic composition of seawater from a number of species. High and variable Nd concentrations in fossil corals however pose the question as to how Nd is incorporated into their skeletons. We here present new results on modern specimens of Desmophyllum dianthus, Balanophyllia malouinensis, and Flabellum curvatum, collected from the Drake Passage, and Madrepora oculata, collected from the North Atlantic. All modern individuals were either collected alive or uranium-series dated to be 〈 500 years old for comparison with local surface sediments and seawater profiles. Modern coral Nd isotopic compositions generally agree with ambient seawater values, which in turn are consistent with previously published seawater analyses, supporting small vertical and lateral Nd isotope gradients in modern Drake Passage waters. Two Balanophyllia malouinensis specimens collected live however deviate by up to 0.6 epsilon units from ambient seawater. We therefore recommend that this species should be treated with caution for the reconstruction of past seawater Nd isotopic compositions. Seventy fossil Drake Passage CWCs were furthermore analysed for their Nd concentrations, revealing a large range from 7.3 to 964.5 ng/g. Samples of the species D. dianthus and Caryophyllia spp. show minor covariation of Nd with 232Th content, utilised to monitor contaminant phases in cleaned coral aragonite. Strong covariations between Nd and Th concentrations are however observed in the species B. malouinensis and G. antarctica. In order to better constrain the source and nature of Nd in the cleaned aragonitic skeletons, a subset of sixteen corals was investigated for its rare earth element (REE) content, as well as major and trace element geochemistry. Our new data provide supporting evidence that the applied cleaning protocol efficiently removes contaminant lithogenic and ferromanganese oxyhydroxide phases. Mass balance calculations and seawater-like REE patterns rule out lithogenic and ferromanganese oxyhydroxide phases as a major contributor to elevated Nd concentrations in coral aragonite. Based on mass balance considerations, geochemical evidence, and previously published independent work by solid-state nuclear magnetic resonance (NMR) spectroscopy, we suggest authigenic phosphate phases as a significant carrier of skeletal Nd. Such a carrier phase could explain sporadic appearance of high Nd concentrations in corals and would be coupled with seawater-derived Nd isotopic compositions, lending further confidence to the application of Nd isotopes as a water mass proxy in CWCs.
    Description: TvdF and TS acknowledge financial support for a bursary by the Grantham Institute of Climate Change and the Environment and a Marie Curie Reintegration grant (IRG 230828), as well as funding from the Leverhulme Trust (RPG-398) and the NERC (NE/N001141/1). Additional financial support was provided to LFR by the USGS-WHOI Co-operative agreement, NSF-ANT grants 0636787 and 80295700, The European Research Council, the Leverhulme Trust and a Marie Curie Reintegration grant. LB was supported by a NOAA/UCAR Climate and Global Change Postdoctoral Fellowship and KJM acknowledges funding from a Marie Curie International Outgoing fellowship (IOF 236962).
    Keywords: Neodymium isotopes ; Rare earth elements ; Cold-water corals ; Seawater ; Sediments ; Drake Passage
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    Inner-shelf ocean dynamics and seafloor morphologic changes during Hurricane Sandy (2017)
    Elsevier
    Details
    Publication Date: 2022-05-25
    Description: This paper is not subject to U.S. copyright. The definitive version was published in Continental Shelf Research 138 (2017): 1-18, doi:10.1016/j.csr.2017.02.003.
    Description: Hurricane Sandy was one of the most destructive hurricanes in US history, making landfall on the New Jersey coast on October 30, 2012. Storm impacts included several barrier island breaches, massive coastal erosion, and flooding. While changes to the subaerial landscape are relatively easily observed, storm-induced changes to the adjacent shoreface and inner continental shelf are more difficult to evaluate. These regions provide a framework for the coastal zone, are important for navigation, aggregate resources, marine ecosystems, and coastal evolution. Here we provide unprecedented perspective regarding regional inner continental shelf sediment dynamics based on both observations and numerical modeling over time scales associated with these types of large storm events. Oceanographic conditions and seafloor morphologic changes are evaluated using both a coupled atmospheric-ocean-wave-sediment numerical modeling system that covered spatial scales ranging from the entire US east coast (1000 s of km) to local domains (10 s of km). Additionally, the modeled response for the region offshore of Fire Island, NY was compared to observational analysis from a series of geologic surveys from that location. The geologic investigations conducted in 2011 and 2014 revealed lateral movement of sedimentary structures of distances up to 450 m and in water depths up to 30 m, and vertical changes in sediment thickness greater than 1 m in some locations. The modeling investigations utilize a system with grid refinement designed to simulate oceanographic conditions with progressively increasing resolutions for the entire US East Coast (5-km grid), the New York Bight (700-m grid), and offshore of Fire Island, NY (100-m grid), allowing larger scale dynamics to drive smaller scale coastal changes. Model results in the New York Bight identify maximum storm surge of up to 3 m, surface currents on the order of 2 ms−1 along the New Jersey coast, waves up to 8 m in height, and bottom stresses exceeding 10 Pa. Flow down the Hudson Shelf Valley is shown to result in convergent sediment transport and deposition along its axis. Modeled sediment redistribution along Fire Island showed erosion across the crests of inner shelf sand ridges and sedimentation in adjacent troughs, consistent with the geologic observations.
    Description: This research was funded by the U.S. Geological Survey (USGS), Coastal and Marine Geology Program, and conducted by the Coastal Change Processes Project. This research was supported in part by the Department of the Interior Hurricane Sandy Recovery program.
    Keywords: Shoreface connected sand ridges ; Sediment transport ; Fire Island, NY ; Hurricane Sandy ; Inner shelf ; Numerical modeling
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    Hydrogeologic controls on chemical transport at Malibu Lagoon, CA : implications for land to sea exchange in coastal lagoon systems (2017)
    Elsevier
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Hydrology: Regional Studies 11 (2017): 219-233, doi:10.1016/j.ejrh.2016.08.003.
    Description: Hydrogeologic controls on seasonal land/sea exchange are investigated in Malibu, California, USA. An assessment of regional groundwater/surface water exchange and associated biogeochemical transport in an intermittently open, coastal lagoon in California is developed using naturally occurring U/Th-series tracers. Nearshore lagoons that are seasonally disconnected from the coastal ocean occupy about 10% of coastal areas worldwide. Lagoon systems often are poorly flushed and thus sensitive to nutrient over-enrichment that can lead to eutrophication, oxygen depletion, and/or pervasive algal blooms. This sensitivity is exacerbated in lagoons that are intermittently closed to surface water exchange with the sea and occur in populous coastal areas. Such estuarine systems are disconnected from the sea during most of the year by wave-built barriers, but during the rainy season these berms can breach, enabling direct water exchange. Using naturally-occurring 222Rn as groundwater tracer, we estimate that groundwater discharge to Malibu Lagoon during open berm conditions was one order of magnitude higher (21 ± 17 cm/day) than during closed berm conditions (1.8 ± 1.4 cm/day). The SGD (submarine groundwater discharge) into nearshore coastal waters at the SurferRider and Colony Malibu was 4.2 cm/day on average. The exported total dissolved nitrogen (TDN) through the berm during closed berm was 1.6 × 10−3 mol/day, whereas during open berm (exported by the Creek) was 3.5 × 103 mol/day. Although these evaluations are specific to the collection campaigns the 2009 and 2010 hydro years, these two distinct hydrologic scenarios play an important role in the seasonality and geochemical impact of land/sea exchange, and highlight the sensitivity of such systems to future impacts such as sea level rise and increasing coastal populations.
    Description: This work was co-funded by the City of Malibu and the U.S. Geological Survey.
    Keywords: Regional groundwater flow ; Submarine groundwater discharge ; Radon ; Hydrologic time series
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    A new Holocene eruptive history of Erebus volcano, Antarctica using cosmogenic 3He and 36Cl exposure ages (2016)
    Elsevier
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Quaternary Geochronology 30 (2015): 114–131, doi:10.1016/j.quageo.2015.09.001.
    Description: The ages of recent effusive eruptions on Erebus volcano, Antarctica are poorly known. Published 40Ar/39Ar ages of the 10 youngest “post-caldera” lava flows are unreliable because of the young ages of the flows (〈10 ka) and the presence of excess 40Ar. Here we use cosmogenic 3He and 36Cl to provide new ages for the 10 youngest flows and 3 older summit flows, including a newly recognized flow distinguished by its exposure age. Estimated eruption ages of the post-caldera flows, assuming no erosion or prior snow cover, range from 4.52 ± 0.08 ka to 8.50 ± 0.19 ka, using Lifton et al. (2014) to scale cosmogenic production rates. If the older Lal (1991)/Stone (2000) model is used to scale production rates, calculated ages are older by 16–25%. Helium-3 and chlorine-36 exposure ages measured on the same samples show excellent agreement. Helium-3 ages measured on clinopyroxene and olivine from the same samples are discordant, probably due in part to lower-than-expected 3He production rates in the Fe-rich olivine. Close agreement of multiple clinopyroxene 3He ages from each flow indicates that the effects of past snow coverage on the exposure ages have been minimal. The new cosmogenic ages differ considerably from published 40Ar/39Ar and 36Cl ages and reveal that the post-caldera flows were erupted during relatively brief periods of effusive activity spread over an interval of ∼4 ka. The average eruption rate over this interval is estimated to be 0.01 km3/ka. Because the last eruption was at least 4 ka ago, and the longest repose interval between the 10 youngest eruptions is ∼1 ka, we consider the most recent period of effusive activity to have ended.
    Description: This research was supported by grant ANT-1142083 from the National Science Foundation, Division of Polar Programs.
    Keywords: Erebus volcano ; Cosmogenic nuclides ; Exposure age ; Helium-3 ; Chlorine-36
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    Corrigendum to “Formation and erosion of the seasonal thermocline in the Kuroshio Extension Recirculation gyre” [Deep-Sea Res. II 85 (2013) 62–74] (2016)
    Elsevier
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    Publication Date: 2022-05-25
    Description: This paper is not subject to U.S. copyright. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 132 (2016): 263–264, doi:10.1016/j.dsr2.2016.08.001.
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    Evaluation of an acoustic remote sensing method for frontal-zone studies using double-diffusive instability microstructure data and density interface data from intrusions (2016)
    Elsevier
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Methods in Oceanography 17 (2016): 264-281, doi:10.1016/j.mio.2016.09.004.
    Description: Understanding intrusive exchange at oceanic water mass fronts may depend on building data-constrained models of the processes, but obtaining the needed representative and comprehensive data is challenging. Acoustic imaging (remote sensing) is an attractive method for mapping the three-dimensional intrusion geometry to enable the required focused in situ sampling of the mixing processes in intrusions. The method depends on backscatter of sound from sharp interfaces and from microstructure resulting from double-diffusive instability (DDI), a probable occurrence at intrusions. The potential of the method is evaluated using data collected using established methods in a field of intrusions south of New England. Above and beneath warm and salty intrusions may lie diffusive–convective DDI microstructure and salt-fingering microstructure, respectively, marking the intrusion boundaries, providing the backscattering features. The data show that both types of microstructure can occur in close proximity within intrusions, but the question of whether this is common or not is unanswered by the modest amount of data, as are questions about continuity of DDI-microstructure in intrusions (to facilitate intrusion acoustic imaging) and variability of DDI-driven heat, salt and buoyancy fluxes. Analysis here shows that detectable backscatter from DDI-microstructure will occur, and can be easily measured when plankton scattering is low enough. Interface scattering is also likely to be detectable. The DDI-linked microstructure data used here are inherently interesting in their own right and are presented in some detail.
    Description: The data were collected under Office of Naval Research grant N00014-03-1-0335. Acoustic analysis was done under grant N00014-14-1-0223/N00014-16-1-2372.
    Keywords: Intrusions ; Double-diffusive microstructure ; Ocean mixing ; Acoustic backscatter ; Echosounder ; South New England shelf
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    Generation of a Xenopus laevis F1 albino J strain by genome editing and oocyte host-transfer (2017)
    Elsevier
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Developmental Biology 426 (2017): 188–193, doi:10.1016/j.ydbio.2016.03.006.
    Description: Completion of the Xenopus laevis genome sequence from inbred J strain animals has facilitated the generation of germline mutant X. laevis using targeted genome editing. In the last few years, numerous reports have demonstrated that TALENs are able to induce mutations in F0 Xenopus embryos, but none has demonstrated germline transmission of such mutations in X. laevis. In this report we used the oocyte host-transfer method to generate mutations in both tyrosinase homeologs and found highly-penetrant germline mutations; in contrast, embryonic injections yielded few germline mutations. We also compared the distribution of mutations in several F0 somatic tissues and germ cells and found that the majority of mutations in each tissue were different. These results establish that X. laevis J strain animals are very useful for generating germline mutations and that the oocyte host-transfer method is an efficient technique for generating mutations in both homeologs.
    Description: This work was supported by grants from the NIH (OD010997 and HD084409).
    Keywords: Xenopus laevis ; TALENs ; J strain ; Tyrosinase ; Oocyte host-transfer ; Genome editing
    Repository Name: Woods Hole Open Access Server
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    Late Cenozoic sea level and the rise of modern rimmed atolls (2016)
    Elsevier
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    Publication Date: 2022-05-25
    Description: This paper is not subject to U.S. copyright. The definitive version was published in Palaeogeography, Palaeoclimatology, Palaeoecology 451 (2016): 73-83, doi:10.1016/j.palaeo.2016.03.018.
    Description: Sea-level records from atolls, potentially spanning the Cenozoic, have been largely overlooked, in part because the processes that control atoll form (reef accretion, carbonate dissolution, sediment transport, vertical motion) are complex and, for many islands, unconstrained on million-year timescales. Here we combine existing observations of atoll morphology and corelog stratigraphy from Enewetak Atoll with a numerical model to (1) constrain the relative rates of subsidence, dissolution and sedimentation that have shaped modern Pacific atolls and (2) construct a record of sea level over the past 8.5 million years. Both the stratigraphy from Enewetak Atoll (constrained by a subsidence rate of ~ 20 m/Myr) and our numerical modeling results suggest that low sea levels (50–125 m below present), and presumably bi-polar glaciations, occurred throughout much of the late Miocene, preceding the warmer climate of the Pliocene, when sea level was higher than present. Carbonate dissolution through the subsequent sea-level fall that accompanied the onset of large glacial cycles in the late Pliocene, along with rapid highstand constructional reef growth, likely drove development of the rimmed atoll morphology we see today.
    Description: Support for this work was provided through a Jackson School Distinguished Postdoctoral Fellowship to Michael Toomey.
    Keywords: Reef ; Coral ; Dissolution ; Late Miocene ; Oxygen isotope stack
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    Analysis of isoform-specific tau aggregates suggests a common toxic mechanism involving similar pathological conformations and axonal transport inhibition (2016)
    Elsevier
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Neurobiology of Aging 47 (2016): 113–126, doi:10.1016/j.neurobiolaging.2016.07.015.
    Description: Misfolded tau proteins are characteristic of tauopathies, but the isoform composition of tau inclusions varies by tauopathy. Using aggregates of the longest tau isoform (containing 4 microtubule-binding repeats and 4-repeat tau), we recently described a direct mechanism of toxicity that involves exposure of the N-terminal phosphatase-activating domain (PAD) in tau, which triggers a signaling pathway that disrupts axonal transport. However, the impact of aggregation on PAD exposure for other tau isoforms was unexplored. Here, results from immunochemical assays indicate that aggregation-induced increases in PAD exposure and oligomerization are common features among all tau isoforms. The extent of PAD exposure and oligomerization was larger for tau aggregates composed of 4-repeat isoforms compared with those made of 3-repeat isoforms. Most important, aggregates of all isoforms exhibited enough PAD exposure to significantly impair axonal transport in the squid axoplasm. We also show that PAD exposure and oligomerization represent common pathological characteristics in multiple tauopathies. Collectively, these results suggest a mechanism of toxicity common to each tau isoform that likely contributes to degeneration in different tauopathies.
    Description: This work was supported by NIH grants R01 AG044372 (Nicholas M. Kanaan), R01 NS082730 (Nicholas M. Kanaan and Scott T. Brady), BrightFocus Foundation (A2013364S, Nicholas M. Kanaan), the Jean P. Schultz Biomedical Research Endowment (Nicholas M. Kanaan), the Secchia Family Foundation (Nicholas M. Kanaan) and NS066942A (Gerardo Morfini).
    Keywords: Tauopathy ; Alzheimer's disease ; Oligomer ; Axon ; Aggregation ; Microtubule-associated protein ; Pathological conformations
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    Changes in substrate availability drive carbon cycle response to chronic warming (2017)
    Elsevier
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Soil Biology and Biochemistry 110 (2017): 68-78, doi:10.1016/j.soilbio.2017.03.002.
    Description: As earth's climate continues to warm, it is important to understand how the capacity of terrestrial ecosystems to retain carbon (C) will be affected. We combined measurements of microbial activity with the concentration, quality, and physical accessibility of soil carbon to microorganisms to evaluate the mechanisms by which more than two decades of experimental warming has altered the carbon cycle in a Northeast US temperate deciduous forest. We found that concentrations of soil organic matter were reduced in both the organic and mineral soil horizons. The molecular composition of the carbon was altered in the mineral soil with significant reductions in the relative abundance of polysaccharides and lignin, and an increase in lipids. Mineral-associated organic matter was preferentially depleted by warming in the top 3 cm of mineral soil. We found that potential extracellular enzyme activity per gram of soil at a common temperature was generally unaffected by warming treatment. However, by measuring potential extracellular enzyme activities between 4 and 30 °C, we found that activity per unit microbial biomass at in-situ temperatures was increased by warming. This was associated with a tendency for microbial biomass to decrease with warming. These results indicate that chronic warming has reduced soil organic matter concentrations, selecting for a smaller but more active microbial community increasingly dependent on mineral-associated organic matter.
    Description: Funding for this project came from Department of Energy Terrestrial Ecosystems Sciences division grant DE-SC0010740 to JMM and KMD. Additional support came from the University of Massachusetts, Amherst, the National Science Foundation Long-Term Ecological Research program (LTER) grant 1237491 to Harvard Forest, and a Sigma Xi grant G20141015649466 to GP.
    Keywords: Soil carbon ; Climate feedbacks ; Enzyme activity ; Microbial adaptation
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    The role of Nrf1 and Nrf2 in the regulation of glutathione and redox dynamics in the developing zebrafish embryo (2017)
    Elsevier
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Redox Biology 13 (2017): 207–218, doi:10.1016/j.redox.2017.05.023.
    Description: Redox signaling is important for embryogenesis, guiding pathways that govern processes crucial for embryo patterning, including cell polarization, proliferation, and apoptosis. Exposure to pro-oxidants during this period can be deleterious, resulting in altered physiology, teratogenesis, later-life diseases, or lethality. We previously reported that the glutathione antioxidant defense system becomes increasingly robust, including a doubling of total glutathione and dynamic shifts in the glutathione redox potential at specific stages during embryonic development in the zebrafish, Danio rerio. However, the mechanisms underlying these changes are unclear, as is the effectiveness of the glutathione system in ameliorating oxidative insults to the embryo at different stages. Here, we examine how the glutathione system responds to the model pro-oxidants tert-butylhydroperoxide and tert-butylhydroquinone at different developmental stages, and the role of Nuclear factor erythroid 2-related factor (Nrf) proteins in regulating developmental glutathione redox status. Embryos became increasingly sensitive to pro-oxidants after 72 h post-fertilization (hpf), after which the duration of the recovery period for the glutathione redox potential was increased. To determine whether the doubling of glutathione or the dynamic changes in glutathione redox potential are mediated by zebrafish paralogs of Nrf transcription factors, morpholino oligonucleotides were used to knock down translation of Nrf1 and Nrf2 (nrf1a, nrf1b, nrf2a, nrf2b). Knockdown of Nrf1a or Nrf1b perturbed glutathione redox state until 72 hpf. Knockdown of Nrf2 paralogs also perturbed glutathione redox state but did not significantly affect the response of glutathione to pro-oxidants. Nrf1b morphants had decreased gene expression of glutathione synthesis enzymes, while hsp70 increased in Nrf2b morphants. This work demonstrates that despite having a more robust glutathione system, embryos become more sensitive to oxidative stress later in development, and that neither Nrf1 nor Nrf2 alone appear to be essential for the response and recovery of glutathione to oxidative insults.
    Description: This research was supported by several NIH grants, including F32ES028085 (to KES), F32ES017585 (to ART-L), F32ES019832 (to LMW), P20GM103423 (to LMW), R01ES025748 (to ART-L), R01ES015912 (JJS), and R01ES016366 (MEH). Additional research support was provided by the J. Seward Johnson Fund at WHOI and the WHOI Postdoctoral Scholar Award with funding from Walter A. and Hope Noyes Smith (to ART-L).
    Keywords: Embryonic development ; Glutathione ; Oxidative stress ; Redox ; Zebrafish ; Antioxidant
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    Development of a coupled wave-flow-vegetation interaction model (2017)
    Elsevier
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Computers & Geosciences 100 (2017): 76–86, doi:10.1016/j.cageo.2016.12.010.
    Description: Emergent and submerged vegetation can significantly affect coastal hydrodynamics. However, most deterministic numerical models do not take into account their influence on currents, waves, and turbulence. In this paper, we describe the implementation of a wave-flow-vegetation module into a Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system that includes a flow model (ROMS) and a wave model (SWAN), and illustrate various interacting processes using an idealized shallow basin application. The flow model has been modified to include plant posture-dependent three-dimensional drag, in-canopy wave-induced streaming, and production of turbulent kinetic energy and enstrophy to parameterize vertical mixing. The coupling framework has been updated to exchange vegetation-related variables between the flow model and the wave model to account for wave energy dissipation due to vegetation. This study i) demonstrates the validity of the plant posture-dependent drag parameterization against field measurements, ii) shows that the model is capable of reproducing the mean and turbulent flow field in the presence of vegetation as compared to various laboratory experiments, iii) provides insight into the flow-vegetation interaction through an analysis of the terms in the momentum balance, iv) describes the influence of a submerged vegetation patch on tidal currents and waves separately and combined, and v) proposes future directions for research and development.
    Description: This study was part of the Estuarine Physical Response to Storms project (GS2-2D), supported by the Department of Interior Hurricane Sandy Recovery program.
    Keywords: Flexible aquatic vegetation ; Coastal hydrodynamics ; Numerical modeling
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    Reply to: Terry, J. and Goff, J. comment on “Late Cenozoic sea level and the rise of modern rimmed atolls” by Toomey et al. (2016), Palaeogeography, Palaeoclimatology, Palaeoecology 451: 73–83 (2017)
    Elsevier
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    Publication Date: 2022-05-25
    Description: This paper is not subject to U.S. copyright. The definitive version was published in Palaeogeography, Palaeoclimatology, Palaeoecology 469 (2017): 159-160, doi:10.1016/j.palaeo.2016.11.028.
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    SyPRID sampler : a large-volume, high-resolution, autonomous, deep-ocean precision plankton sampling system (2017)
    Elsevier
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 137 (2017): 297–306, doi:10.1016/j.dsr2.2016.05.007.
    Description: The current standard for large-volume (thousands of cubic meters) zooplankton sampling in the deep sea is the MOCNESS, a system of multiple opening–closing nets, typically lowered to within 50 m of the seabed and towed obliquely to the surface to obtain low-spatial-resolution samples that integrate across 10 s of meters of water depth. The SyPRID (Sentry Precision Robotic Impeller Driven) sampler is an innovative, deep-rated (6000 m) plankton sampler that partners with the Sentry Autonomous Underwater Vehicle (AUV) to obtain paired, large-volume plankton samples at specified depths and survey lines to within 1.5 m of the seabed and with simultaneous collection of sensor data. SyPRID uses a perforated Ultra-High-Molecular-Weight (UHMW) plastic tube to support a fine mesh net within an outer carbon composite tube (tube-within-a-tube design), with an axial flow pump located aft of the capture filter. The pump facilitates flow through the system and reduces or possibly eliminates the bow wave at the mouth opening. The cod end, a hollow truncated cone, is also made of UHMW plastic and includes a collection volume designed to provide an area where zooplankton can collect, out of the high flow region. SyPRID attaches as a saddle-pack to the Sentry vehicle. Sentry itself is configured with a flight control system that enables autonomous survey paths to low altitudes. In its verification deployment at the Blake Ridge Seep (2160 m) on the US Atlantic Margin, SyPRID was operated for 6 h at an altitude of 5 m. It recovered plankton samples, including delicate living larvae, from the near-bottom stratum that is seldom sampled by a typical MOCNESS tow. The prototype SyPRID and its next generations will enable studies of plankton or other particulate distributions associated with localized physico-chemical strata in the water column or above patchy habitats on the seafloor.
    Description: This work is part of the SeepC Project funded by the National Science Foundation through OCE-1031050 (Van Dover) and 1030453 (Young), together with funds for development of SyPRID and Sentry operations (OCE-1036843; A Bowen, WHOI).
    Keywords: Plankton surveys ; Meroplankton ; Deep water
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    Benthic storms, nepheloid layers, and linkage with upper ocean dynamics in the western North Atlantic (2017)
    Elsevier
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marine Geology 385 (2017): 304–327, doi:10.1016/j.margeo.2016.12.012.
    Description: Benthic storms are episodic periods of strong abyssal currents and intense, benthic nepheloid (turbid) layer development. In order to interpret the driving forces that create and sustain these storms, we synthesize measurements of deep ocean currents, nephelometer-based particulate matter (PM) concentrations, and seafloor time-series photographs collected during several science programs that spanned two decades in the western North Atlantic. Benthic storms occurred in areas with high sea-surface eddy kinetic energy, and they most frequently occurred beneath the meandering Gulf Stream or its associated rings, which generate deep cyclones, anticyclones, and/or topographic waves; these create currents with sufficient bed-shear stress to erode and resuspend sediment, thus initiating or enhancing benthic storms. Occasionally, strong currents do not correspond with large increases in PM concentrations, suggesting that easily erodible sediment was previously swept away. Periods of moderate to low currents associated with high PM concentrations are also observed; these are interpreted as advection of PM delivered as storm tails from distal storm events. Outside of areas with high surface and deep eddy kinetic energy, benthic nepheloid layers are weak to non-existent, indicating that benthic storms are necessary to create and maintain strong nepheloid layers. Origins and intensities of benthic storms are best identified using a combination of time-series measurements of bottom currents, PM concentration, and bottom photographs, and these should be coupled with water-column and surface-circulation data to better interpret the specific relations between shallow and deep circulation patterns. Understanding the generation of benthic nepheloid layers is necessary in order to properly interpret PM distribution and its influence on global biogeochemistry.
    Description: Funding for construction of the Bottom Ocean Monitor was provided by Lamont-Doherty Geological Observatory (now Lamont-Doherty Earth Observatory). BOM and mooring deployments and data analysis were funded by the Office of Naval Research (contracts N00014-75-C-0210 and N00014-80-C-0098 to Biscaye and Gardner at Lamont-Doherty; Contracts N00014-79-C-0071 and N00014-82-C-0019 at Woods Hole Oceanographic Institution and ONR Contracts N00014-75-C-0210 and N00014-80-C-0098 at Lamont-Doherty Geological Observatory to Tucholke), Sandia National Laboratories (contract SL-16-5279 to Gardner), the National Science Foundation (contract OCE 1536565 to Gardner and Richardson), Earl F. Cook Professorship (Gardner), and the Department of Energy (contract DE-FG02-87ER-60555 to Biscaye).
    Keywords: Benthic storms ; Benthic nepheloid layer ; Abyssal currents ; Seafloor erosion ; Eddy kinetic energy ; Cyclogenesis
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    Environmental metabolomics : databases and tools for data analysis (2016)
    Elsevier
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marine Chemistry 177 (2015): 366–373, doi:10.1016/j.marchem.2015.06.012.
    Description: Metabolomics is the study of small molecules, or ‘metabolites’, that are the end products of biological processes. While -omics technologies such as genomics, transcriptomics, and proteomics measure the metabolic potential of organisms, metabolomics provides detailed information on the organic compounds produced during metabolism and found within cells and in the environment. Improvements in analytical techniques have expanded our understanding of metabolomics and developments in computational tools have made metabolomics data accessible to a broad segment of the scientific community. Yet, metabolomics methods have only been applied to a limited number of projects in the marine environment. Here, we review analysis techniques for mass spectrometry data and summarize the current state of metabolomics databases. We then describe a boutique database developed in our laboratory for efficient data analysis and selection of mass spectral targets for metabolite identification. The code to implement the database is freely available on GitHub (https://github.com/joefutrelle/domdb). Data organization and analysis are critical, but often under-appreciated, components of metabolomics research. Future advances in environmental metabolomics will take advantage of continued development of new tools that facilitate analysis of large metabolomics datasets.
    Description: The field data populating the database comes from scientific cruises funded by grants from the National Science Foundation to EBK and KL (Atlantic Ocean, OCE-1154320) and E.V. Armbrust (Pacific Ocean, OCE-1205233). The laboratory experiment with coastal seawater was funded by a grant from the Gulf of Mexico Research Initiative to EBK and H.K. White. The laboratory experiments with microbial isolates and the database development are funded by the Gordon and Betty Moore Foundation through Grant GBMF3304 to EBK.
    Keywords: Metabolomics ; Data analysis ; Database design
    Repository Name: Woods Hole Open Access Server
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    Decoupling processes and scales of shoreline morphodynamics (2016)
    Elsevier
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    Publication Date: 2022-05-25
    Description: This paper is not subject to U.S. copyright. The definitive version was published in Marine Geology 381 (2016): 42–53, doi:10.1016/j.margeo.2016.08.008.
    Description: Behavior of coastal systems on time scales ranging from single storm events to years and decades is controlled by both small-scale sediment transport processes and large-scale geologic, oceanographic, and morphologic processes. Improved understanding of coastal behavior at multiple time scales is required for refining models that predict potential erosion hazards and for coastal management planning and decision-making. Here we investigate the primary controls on shoreline response along a geologically-variable barrier island on time scales resolving extreme storms and decadal variations over a period of nearly one century. An empirical orthogonal function analysis is applied to a time series of shoreline positions at Fire Island, NY to identify patterns of shoreline variance along the length of the island. We establish that there are separable patterns of shoreline behavior that represent response to oceanographic forcing as well as patterns that are not explained by this forcing. The dominant shoreline behavior occurs over large length scales in the form of alternating episodes of shoreline retreat and advance, presumably in response to storms cycles. Two secondary responses include long-term response that is correlated to known geologic variations of the island and the other reflects geomorphic patterns with medium length scale. Our study also includes the response to Hurricane Sandy and a period of post-storm recovery. It was expected that the impacts from Hurricane Sandy would disrupt long-term trends and spatial patterns. We found that the response to Sandy at Fire Island is not notable or distinguishable from several other large storms of the prior decade.
    Description: Funding for this research was provided by the USGS Coastal and Marine Geology Program and the USGS Natural Resource Preservation Program.
    Keywords: Shoreline change ; Coastal evolution ; Storm response ; Empirical orthogonal function ; Fire Island
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    Stochasticity, heterogeneity, and variance in longevity in human populations (2017)
    Elsevier
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Theoretical Population Biology 114 (2017): 107-116, doi:10.1016/j.tpb.2017.01.001.
    Description: Inter-individual variance in longevity (or any other demographic outcome) may arise from heterogeneity or from individual stochasticity. Heterogeneity refers to differences among individuals in the demographic rates experienced at a given age or stage. Stochasticity refers to variation due to the random outcome of demographic rates applied to individuals with the same properties. The variance due to individual stochasticity can be calculated from a Markov chain description of the life cycle. The variance due to heterogeneity can be calculated from a multistate model that incorporates the heterogeneity. We show how to use this approach to decompose the variance in longevity into contributions from stochasticity and heterogeneous frailty for male and female cohorts from Sweden (1751–1899), France (1816–1903), and Italy (1872–1899), and also for a selection of period data for the same countries. Heterogeneity in mortality is described by the gamma-Gompertz–Makeham model, in which a gamma distributed “frailty” modifies a baseline Gompertz–Makeham mortality schedule. Model parameters were estimated by maximum likelihood for a range of starting ages. The estimates were used to construct an age××frailty-classified matrix model, from which we compute the variance of longevity and its components due to heterogeneous frailty and to individual stochasticity. The estimated fraction of the variance in longevity due to heterogeneous frailty (averaged over time) is less than 10% for all countries and for both sexes. These results suggest that most of the variance in human longevity arises from stochasticity, rather than from heterogeneous frailty.
    Description: This work was supported by European Research Council Advanced Grant 322989 (to NH and HC), National Science Foundation Grant DEB-1257545 (to HC), and the Max Planck Society (to TIM).
    Keywords: Individual stochasticity ; Heterogeneous frailty ; Variance ; Longevity ; Age–frailty classified matrix model ; Gamma-Gompertz–Makeham
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    Utility of Rn-222 as a passive tracer of subglacial distributed system drainage (2017)
    Elsevier
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    Publication Date: 2022-05-25
    Description: This paper is not subject to U.S. copyright. The definitive version was published in Earth and Planetary Science Letters 462 (2017): 180-188, doi:10.1016/j.epsl.2016.12.039.
    Description: Water flow beneath the Greenland Ice Sheet (GrIS) has been shown to include slow-inefficient (distributed) and fast-efficient (channelized) drainage systems, in response to meltwater delivery to the bed via both moulins and surface lake drainage. This partitioning between channelized and distributed drainage systems is difficult to quantify yet it plays an important role in bulk meltwater chemistry and glacial velocity, and thus subglacial erosion. Radon-222, which is continuously produced via the decay of 226Ra, accumulates in meltwater that has interacted with rock and sediment. Hence, elevated concentrations of 222Rn should be indicative of meltwater that has flowed through a distributed drainage system network. In the spring and summer of 2011 and 2012, we made hourly 222Rn measurements in the proglacial river of a large outlet glacier of the GrIS (Leverett Glacier, SW Greenland). Radon-222 activities were highest in the early melt season (10–15 dpm L−1), decreasing by a factor of 2–5 (3–5 dpm L−1) following the onset of widespread surface melt. Using a 222Rn mass balance model, we estimate that, on average, greater than 90% of the river 222Rn was sourced from distributed system meltwater. The distributed system 222Rn flux varied on diurnal, weekly, and seasonal time scales with highest fluxes generally occurring on the falling limb of the hydrograph and during expansion of the channelized drainage system. Using laboratory based estimates of distributed system 222Rn, the distributed system water flux generally ranged between 1–5% of the total proglacial river discharge for both seasons. This study provides a promising new method for hydrograph separation in glacial watersheds and for estimating the timing and magnitude of distributed system fluxes expelled at ice sheet margins.
    Description: U.S. National Science Foundation Arctic Natural Sciences Program (ANS-1256669); Woods Hole Oceanographic Institution Arctic Research Initiative, Ocean Ventures Fund, and Ocean Climate Change Institute; United Kingdom Natural Environment Research Council studentship (NE/152830X/1); the Carnegie Trust, Edinburgh University Development Trust.
    Keywords: Radon ; Greenland ; Glacier ; Proglacial river ; Meltwater
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    Seismic evidence of glacial-age river incision into the Tahaa barrier reef, French Polynesia (2016)
    Elsevier
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    Publication Date: 2022-05-25
    Description: This paper is not subject to U.S. copyright. The definitive version was published in Marine Geology 380 (2016): 284–289, doi:10.1016/j.margeo.2016.04.008.
    Description: Rivers have long been recognized for their ability to shape reef-bound volcanic islands. On the time-scale of glacial–interglacial sea-level cycles, fluvial incision of exposed barrier reef lagoons may compete with constructional coral growth to shape the coastal geomorphology of ocean islands. However, overprinting of Pleistocene landscapes by Holocene erosion or sedimentation has largely obscured the role lowstand river incision may have played in developing the deep lagoons typical of modern barrier reefs. Here we use high-resolution seismic imagery and core stratigraphy to examine how erosion and/or deposition by upland drainage networks has shaped coastal morphology on Tahaa, a barrier reef-bound island located along the Society Islands hotspot chain in French Polynesia. At Tahaa, we find that many channels, incised into the lagoon floor during Pleistocene sea-level lowstands, are located near the mouths of upstream terrestrial drainages. Steeper antecedent topography appears to have enhanced lowstand fluvial erosion along Tahaa's southwestern coast and maintained a deep pass. During highstands, upland drainages appear to contribute little sediment to refilling accommodation space in the lagoon. Rather, the flushing of fine carbonate sediment out of incised fluvial channels by storms and currents appears to have limited lagoonal infilling and further reinforced development of deep barrier reef lagoons during periods of highstand submersion.
    Description: This project was supported by a Jackson School Distinguished Postdoctoral Fellowship to Michael Toomey and the WHOI Coastal Ocean Institute and Ocean and Climate Change Institute.
    Keywords: Coral ; Island ; Lagoon ; Dissolution ; Morphology
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    Luteinizing Hormone is an effective replacement for hCG to induce ovulation in Xenopus (2017)
    Elsevier
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Developmental Biology 426 (2017): 442–448, doi:10.1016/j.ydbio.2016.05.028.
    Description: Injection of human Chorionic Gonadotropin (hCG) directly into the dorsal lymph sac of Xenopus is a commonly used protocol for induction of ovulation, but recent shortages in the stocks of commercially available hCG as well as lack of a well tested alternative have resulted in frustrating experimental delays in laboratories that predominantly use Xenopus in their research. Mammalian Luteinizing Hormones (LH) share structural similarity, functional equivalency, and bind the same receptor as hCG; this suggests that LH may serve as a good alternative to hCG for promoting ovulation in Xenopus. LH has been found to induce maturation of Xenopus oocytes in vitro, but whether it can be used to induce ovulation in vivo has not been examined. Here we compared the ability of four mammalian LH proteins, bovine (bLH), human (hLH), ovine (oLH), porcine (pLH), to induce ovulation in Xenopus when injected into the dorsal lymph sac of sexually mature females. We find that both ovine and human LH, but not bovine or porcine, are good substitutes for hCG for induction of ovulation in WT and J strain Xenopus laevis and Xenopus tropicalis.
    Description: This work was supported by a grant from the NIHP40OD010997.
    Keywords: Xenopus laevis ; J strain ; Luteinizing Hormone ; Ovulation ; Chorionic gonadotropin
    Repository Name: Woods Hole Open Access Server
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  • 77
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    Expanding the genetic toolkit in Xenopus : approaches and opportunities for human disease modeling (2017)
    Elsevier
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Developmental Biology 426 (2017): 325-335, doi:10.1016/j.ydbio.2016.04.009.
    Description: The amphibian model Xenopus, has been used extensively over the past century to study multiple aspects of cell and developmental biology. Xenopus offers advantages of a non-mammalian system, including high fecundity, external development, and simple housing requirements, with additional advantages of large embryos, highly conserved developmental processes, and close evolutionary relationship to higher vertebrates. There are two main species of Xenopus used in biomedical research, Xenopus laevis and Xenopus tropicalis; the common perception is that both species are excellent models for embryological and cell biological studies, but only Xenopus tropicalis is useful as a genetic model. The recent completion of the Xenopus laevis genome sequence combined with implementation of genome editing tools, such as TALENs (transcription activator-like effector nucleases) and CRISPR-Cas (clustered regularly interspaced short palindromic repeats-CRISPR associated nucleases), greatly facilitates the use of both Xenopus laevis and Xenopus tropicalis for understanding gene function in development and disease. In this paper, we review recent advances made in Xenopus laevis and Xenopus tropicalis with TALENs and CRISPR-Cas and discuss the various approaches that have been used to generate knockout and knock-in animals in both species. These advances show that both Xenopus species are useful for genetic approaches and in particular counters the notion that Xenopus laevis is not amenable to genetic manipulations.
    Description: This work was supported by the National Institutes of Health (P40 OD010997 to M.E.H., R01 HD084409 to M.E.H., R01 HL112618 to P.T. and F.C., and R01 HL127640 to P.T. and F.C.; and the U.S. Environmental Protection Agency (G11E10367 to D.F.).
    Keywords: CRISPR-Cas ; TALENs ; J strain ; Xenopus laevis ; Xenopus tropicalis ; Knock-in ; Human disease model
    Repository Name: Woods Hole Open Access Server
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    Relationship between water and aragonite barium concentrations in aquaria reared juvenile corals (2017)
    Elsevier
    Details
    Publication Date: 2022-05-25
    Description: This paper is not subject to U.S. copyright. The definitive version was published in Geochimica et Cosmochimica Acta 209 (2017): 123-134, doi:10.1016/j.gca.2017.04.006.
    Description: Coral barium to calcium (Ba/Ca) ratios have been used to reconstruct records of upwelling, river and groundwater discharge, and sediment and dust input to the coastal ocean. However, this proxy has not yet been explicitly tested to determine if Ba inclusion in the coral skeleton is directly proportional to seawater Ba concentration and to further determine how additional factors such as temperature and calcification rate control coral Ba/Ca ratios. We measured the inclusion of Ba within aquaria reared juvenile corals (Favia fragum) at three temperatures (∼27.7, 24.6 and 22.5 °C) and three seawater Ba concentrations (73, 230 and 450 nmol kg−1). Coral polyps were settled on tiles conditioned with encrusting coralline algae, which complicated chemical analysis of the coral skeletal material grown during the aquaria experiments. We utilized Sr/Ca ratios of encrusting coralline algae (as low as 3.4 mmol mol−1) to correct coral Ba/Ca for this contamination, which was determined to be 26 ± 11% using a two end member mixing model. Notably, there was a large range in Ba/Ca across all treatments, however, we found that Ba inclusion was linear across the full concentration range. The temperature sensitivity of the distribution coefficient is within the range of previously reported values. Finally, calcification rate, which displayed large variability, was not correlated to the distribution coefficient. The observed temperature dependence predicts a change in coral Ba/Ca ratios of 1.1 μmol mol−1 from 20 to 28 °C for typical coastal ocean Ba concentrations of 50 nmol kg−1. Given the linear uptake of Ba by corals observed in this study, coral proxy records that demonstrate peaks of 10–25 μmol mol−1 would require coastal seawater Ba of between 60 and 145 nmol kg−1. Further validation of the coral Ba/Ca proxy requires evaluation of changes in seawater chemistry associated with the environmental perturbation recorded by the coral as well as verification of these results for Porites species, which are widely used in paleo reconstructions.
    Description: M.E.G. was supported by a NDSEG graduate fellowship. Funding for this research came from the NSF Chemical Oceanography program (OCE-0751525) and the Coastal Ocean Institute, the Ocean and Climate Change Institute and the Ocean Ventures Fund at Woods Hole Oceanographic Institution.
    Keywords: Coral Ba/Ca ; Barium ; Aragonite ; Distribution coefficient ; Favia fragum
    Repository Name: Woods Hole Open Access Server
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    Continental-scale homogenization of residential lawn plant communities (2017)
    Elsevier
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Landscape and Urban Planning 165 (2017): 54-63, doi:10.1016/j.landurbplan.2017.05.004.
    Description: Residential lawns are highly managed ecosystems that occur in urbanized landscapes across the United States. Because they are ubiquitous, lawns are good systems in which to study the potential homogenizing effects of urban land use and management together with the continental-scale effects of climate on ecosystem structure and functioning. We hypothesized that similar homeowner preferences and management in residential areas across the United States would lead to low plant species diversity in lawns and relatively homogeneous vegetation across broad geographical regions. We also hypothesized that lawn plant species richness would increase with regional temperature and precipitation due to the presence of spontaneous, weedy vegetation, but would decrease with household income and fertilizer use. To test these predictions, we compared plant species composition and richness in residential lawns in seven U.S. metropolitan regions. We also compared species composition in lawns with understory vegetation in minimally-managed reference areas in each city. As expected, the composition of cultivated turfgrasses was more similar among lawns than among reference areas, but this pattern also held among spontaneous species. Plant species richness and diversity varied more among lawns than among reference areas, and more diverse lawns occurred in metropolitan areas with higher precipitation. Native forb diversity increased with precipitation and decreased with income, driving overall lawn diversity trends with these predictors as well. Our results showed that both management and regional climate shaped lawn species composition, but the overall homogeneity of species regardless of regional context strongly suggested that management was a more important driver.
    Description: This research was supported by the Macrosystems Biology Program in the Emerging Frontiers Division of the Biological Sciences Directorate at the National Science Foundation (NSF) under grants EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831, and 121238320.
    Keywords: Homogenization ; Lawn ; Residential yards ; Species composition ; Turfgrass
    Repository Name: Woods Hole Open Access Server
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    Observations of nearshore groundwater discharge : Kahekili Beach Park submarine springs, Maui, Hawaii (2017)
    Elsevier
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Hydrology: Regional Studies 11 (2017): 147-165, doi:10.1016/j.ejrh.2015.12.056.
    Description: The study region encompasses the nearshore, coastal waters off west Maui, Hawaii. Here abundant groundwater—that carries with it a strong land-based fingerprint—discharges into the coastal waters and over a coral reef. Coastal groundwater discharge is a ubiquitous hydrologic feature that has been shown to impact nearshore ecosystems and material budgets. A unique combined geochemical tracer and oceanographic time-series study addressed rates and oceanic forcings of submarine groundwater discharge at a submarine spring site off west Maui, Hawaii. Estimates of submarine groundwater discharge were derived for a primary vent site and surrounding coastal waters off west Maui, Hawaii using an excess 222Rn (t1/2 = 3.8 d) mass balance model. Such estimates were complemented with a novel thoron (220Rn, t1/2 = 56 s) groundwater discharge tracer application, as well as oceanographic time series and thermal infrared imagery analyses. In combination, this suite of techniques provides new insight into the connectivity of the coastal aquifer with the near-shore ocean and examines the physical drivers of submarine groundwater discharge. Lastly, submarine groundwater discharge derived constituent concentrations were tabulated and compared to surrounding seawater concentrations. Such work has implications for the management of coastal aquifers and downstream nearshore ecosystems that respond to sustained constituent loadings via this submarine route.
    Description: This research was primarily funded by the USGS Coastal and Marine Geology Program (CMGP). CRG acknowledges support from the National Oceanic and Atmospheric Administration, Project R/SB-12, which is sponsored by the University of Hawaii Sea Grant College Program, SOEST, under Institutional Grant No. NA14OAR4170071 from NOAA Office of Sea Grant, Department of Commerce.
    Keywords: Regional groundwater flow ; Submarine groundwater discharge ; Radon ; Thoron ; Thermal infrared ; Oceanographic time series ; Salinity
    Repository Name: Woods Hole Open Access Server
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    Clumped isotope composition of cold-water corals : a role for vital effects? (2016)
    Elsevier
    Details
    Publication Date: 2016-09-23
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Geochimica et Cosmochimica Acta 179 (2016): 123-141, doi:10.1016/j.gca.2016.01.023.
    Description: The carbonate clumped isotope thermometer is a promising tool for determining past ocean temperatures. It is based on the temperature dependence of rare isotopes ‘clumping’ into the same carbonate ion group in the carbonate mineral lattice. The extent of this clumping effect is independent of the isotope composition of the water from which carbonate precipitates, providing unique advantages over many other paleotemperature proxies. Existing calibrations of this thermometer in cold-water and warm-water corals suggest clumped isotope ‘vital effects’ are negligible in cold-water corals but may be significant in warm-water corals. Here, we test the calibration of the carbonate clumped isotope thermometer in cold-water corals with a recently collected and well characterised sample set spanning a range of coral genera (Balanophyllia, Caryophyllia, Dasmosmilia, Desmophyllum, Enallopsammia and Javania). The clumped isotope compositions (Δ47) of these corals exhibit systematic dependences on their growth temperatures, confirming the basis of the carbonate clumped isotope thermometer. However, some cold-water coral genera show Δ47 values that are higher than the expected equilibrium values by up to 0.05‰ (equivalent to underestimating temperature by ∼9 °C) similar to previous findings for some warm-water corals. This finding suggests that the vital effects affecting corals Δ47 are common to both warm- and cold-water corals. By comparison with models of the coral calcification process we suggest that the clumped isotope offsets in these genera are related to the kinetic isotope effects associated with CO2 hydration/hydroxylation reactions in the corals’ calcifying fluid. Our findings complicate the use of the carbonate clumped isotope thermometer in corals, but suggest that species- or genus-specific calibrations could be useful for the future application of this paleotemperature proxy.
    Description: This work was supported by a British National Environment Research Council studentship to P. Spooner (NE/K500823/1), National Science Foundation Grant NSF-ANT-1246387 and The Penzance Endowed Fund in Support of Assistant Scientists (WHOI) to W. Guo, and by funds from the European Research Council, the Leverhulme Trust and a Marie Curie Reintegration grant.
    Repository Name: Woods Hole Open Access Server
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    Impact of climate warming on snow processes in Ny-Ålesund, a polar maritime site at Svalbard (2016)
    Elsevier
    In:  EPIC3Global and Planetary Change, Elsevier, 146, pp. 10-21, ISSN: 09218181
    Details
    Publication Date: 2021-08-20
    Description: The impact of observed changes in air temperature and precipitation from 1969 to 2013 and climate projections for 2050 and 2080 at Ny-Ålesund, an arctic research station on Spitzbergen Island in the Svalbard Archipelago on snow hydrological processes, were analyzed using snow accumulation and ablation algorithms in the physically based Cold Regions HydrologicalModelling platform(CRHM). The climate projectionswere obtained from phase 5 of the Coupled Model Intercomparison Project (CMIP5), with a focus on the snow-dominated period (October to June). To identify the potential effects of increasing temperature and precipitation, a model sensitivity analysis (1 °C to 5 °C), with and without a 25% increase in precipitation, was run on CRHM snow processes. The results indicated that the greatest observed warming was during the early snow season (October–February), with increases of 0.8 and 0.9 °C decade−1 for maximum (Tmax) and minimum (Tmin) temperatures, respectively. Therewas also a significant increase in annual and winter precipitation (24mmdecade−1). The late snowseason (March–June) also had a marked increase in temperature (0.5 and 0.69 °C decade−1 for Tmax and Tmin respectively), but no significant change in precipitation. These changes lead to a significant increase in the number of dayswith rainfall rather than snowfall. The sensitivity analysis indicated that mean snowwater equivalent snowpack will decrease by 10.2% (early snow season) and 11.1% (late snow season) per degree of increased air temperature. For each degree of temperature increase, the modelled peak snow-water-equivalent (SWE) declined by 6.9%, duration of snowpack declined 11 days, and the number of days with rain increased 43% for the early snow season and 12.8% for the late snowseason. Awarmer climate also leads to markedly decreased surface snowsublimation and the fraction of snowfall eroded and transported by blowing snow. For most snowpack parameters analyzed, the response to warming accelerates with increased warming, especially above 3 °C. A 25% increase in precipitation partially counteracted the response to warming, with the greatest effect on peak SWE.
    Repository Name: EPIC Alfred Wegener Institut
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  • 83
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    Embryos, microscopes, and society (2016)
    Elsevier
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Studies in History and Philosophy of Science Part C: Studies in History and Philosophy of Biological and Biomedical Sciences 57 (2016): 129-136, doi:10.1016/j.shpsc.2016.02.003.
    Description: Embryos have different meanings for different people and in different contexts. Seen under the microscope, the biological embryo starts out as one cell and then becomes a bunch of cells. Gradually these divide and differentiate to make up the embryo, which in humans becomes a fetus at eight weeks, and then eventually a baby. At least, that happens in those cases that carry through normally and successfully. Yet a popular public perception imagines the embryo as already a little person in the very earliest stages of development, as if it were predictably to become an adult. In actuality, cells can combine, pull apart, and recombine in a variety of ways and still produce embryos, whereas most embryos never develop into adults at all. Biological embryos and popular imaginations of embryos diverge. This paper looks at some of the historical reasons for and social implications of that divergence.
    Description: Thanks to the National Science Foundation for support through a series of grants.
    Keywords: Embryos ; Microscopes ; Science and society ; Bioethics ; Science policy
    Repository Name: Woods Hole Open Access Server
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    Biological effects of 6-formylindolo[3,2-b]carbazole (FICZ) in vivo are enhanced by loss of CYP1A function in an Ahr2-dependent manner (2016)
    Elsevier
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Biochemical Pharmacology 110-111 (2016): 117-129, doi:10.1016/j.bcp.2016.04.012.
    Description: 6-Formylindolo[3,2-b]carbazole (FICZ) is a potent aryl hydrocarbon receptor (AHR) agonist that is efficiently metabolized by AHR-regulated cytochrome P4501 enzymes. FICZ is a proposed physiological AHR ligand that induces its own degradation as part of a regulatory negative feedback loop. In vitro studies in cells show that CYP1 inhibition in the presence of FICZ results in enhanced AHR activation, suggesting that FICZ accumulates in the cell when its metabolism is blocked. We used zebrafish (Danio rerio) embryos to investigate the in vivo effects of FICZ when CYP1A is knocked down or inhibited. Embryos were injected with morpholino antisense oligonucleotides targeting CYP1A (CYP1A-MO), Ahr2, or a combination of both. FICZ exposure of non-injected embryos or embryos injected with control morpholino had little effect. In CYP1A-MO-injected embryos, however, FICZ dramatically increased mortality, incidence and severity of pericardial edema and circulation failure, reduced hatching frequency, blocked swim bladder inflation, and strongly potentiated expression of Ahr2-regulated genes. These effects were substantially reduced in embryos with a combined knockdown of Ahr2 and CYP1A, indicating that the toxicity was mediated at least partly by Ahr2. Co-exposure to the CYP1 inhibitor alpha-naphthoflavone (αNF) and FICZ had similar effects as the combination of CYP1A-MO and FICZ. HPLC analysis of FICZ-exposed embryos showed increased levels of FICZ after concomitant CYP1A-MO injection or αNF co-exposure. Together, these results show that a functioning CYP1/AHR feedback loop is crucial for regulation of AHR signaling by a potential physiological ligand in vivo and further highlights the role of CYP1 enzymes in regulating biological effects of FICZ.
    Description: This work was supported by Swedish Research Council Formas grants 2011-963 (EW) and 2008-1249 (MJ), by a European Commission Horizon 2020 grant, Project ID 634880 (MJ), by a National Institute of Environmental Health Sciences (NIEHS) grant P42ES007381 (JJS and MEH), R01ES006272 (MEH) and F32ES017585 (ART-L), by Japan Society for the Promotion of Science Postdoctoral Fellowship for Research Abroad194313 (AK), by Grant-in-Aids for Research Activity Start-up26881001 (AK) and for Young Scientists (A)15H05334 (AK).
    Keywords: Aryl hydrocarbon receptor ; Cytochrome P4501 ; 6-Formylindolo[3,2-b]carbazole ; Enzyme inhibition ; Zebrafish embryo toxicity ; Synergistic receptor activation
    Repository Name: Woods Hole Open Access Server
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  • 85
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    Defining planktonic protist functional groups on mechanisms for energy and nutrient acquisition : incorporation of diverse mixotrophic strategies (2016)
    Elsevier
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Protist 167 (2016): 106–120, doi:10.1016/j.protis.2016.01.003.
    Description: Arranging organisms into functional groups aids ecological research by grouping organisms (irrespective of phylogenetic origin) that interact with environmental factors in similar ways. Planktonic protists traditionally have been split between photoautotrophic “phytoplankton” and phagotrophic “microzooplankton”. However, there is a growing recognition of the importance of mixotrophy in euphotic aquatic systems, where many protists often combine photoautotrophic and phagotrophic modes of nutrition. Such organisms do not align with the traditional dichotomy of phytoplankton and microzooplankton. To reflect this understanding, we propose a new functional grouping of planktonic protists in an eco-physiological context: (i) phagoheterotrophs lacking phototrophic capacity, (ii) photoautotrophs lacking phagotrophic capacity, (iii) constitutive mixotrophs (CMs) as phagotrophs with an inherent capacity for phototrophy, and (iv) non-constitutive mixotrophs (NCMs) that acquire their phototrophic capacity by ingesting specific (SNCM) or general non-specific (GNCM) prey. For the first time, we incorporate these functional groups within a foodweb structure and show, using model outputs, that there is scope for significant changes in trophic dynamics depending on the protist functional type description. Accordingly, to better reflect the role of mixotrophy, we recommend that as important tools for explanatory and predictive research, aquatic food-web and biogeochemical models need to redefine the protist groups within their frameworks.
    Description: This work was funded by grants to KJF and AM from the Leverhulme Trust (International Network Grant F00391 V) and NERC (UK) through its iMARNET programme NE/K001345/1.
    Keywords: Plankton functional types (PFTs) ; Phagotroph ; Phototroph ; Mixotroph ; Phytoplankton ; Microzooplankton
    Repository Name: Woods Hole Open Access Server
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  • 86
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    Preliminary Geochemical and Isotopic Results in Thermal and Cold Waters of Graciosa Volcanic Island (Azores) (2017)
    Elsevier
    Details
    Publication Date: 2022-06-08
    Description: Graciosa Island is located in the Azores Archipelago, along the so-called Terceira Rift, NE boundary of the Azores Plateau. From the hydrochemical point of view, two types of Na-Cl groundwater systems were identified: a cold aquifer system emerging at springs and exploited through boreholes for public water supply with different degrees of mineralization, and a hydrothermal system with issuing temperatures around 45 ºC. Geothermometers applied to the thermal waters point to deep temperature around 167 ºC and to immature waters, not reaching complete equilibrium with the reservoir rock. The isotopic composition and geochemistry of the thermal waters indicate mixture groundwater - seawater in different percentages and ion-exchange mechanisms that will be able to: i) increase groundwater salinity, ii) strongly change the isotopic composition to more enriched values, with different degrees of mixing.
    Description: Published
    Description: 630-633
    Description: 2V. Struttura e sistema di alimentazione dei vulcani
    Description: N/A or not JCR
    Keywords: Thermal waters ; Volcanic island ; seawater-groundwater mixture ; Azores (Portugal) ; 03.02. Hydrology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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    The GEOTRACES Intermediate Data Product 2014 (2016)
    Elsevier
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marine Chemistry 177 (2015): 1-8, doi:10.1016/j.marchem.2015.04.005.
    Description: The GEOTRACES Intermediate Data Product 2014 (IDP2014) is the first publicly available data product of the international GEOTRACES programme, and contains data measured and quality controlled before the end of 2013. It consists of two parts: (1) a compilation of digital data for more than 200 trace elements and isotopes (TEIs) as well as classical hydrographic parameters, and (2) the eGEOTRACES Electronic Atlas providing a strongly inter-linked on-line atlas including more than 300 section plots and 90 animated 3D scenes. The IDP2014 covers the Atlantic, Arctic, and Indian oceans, exhibiting highest data density in the Atlantic. The TEI data in the IDP2014 are quality controlled by careful assessment of intercalibration results and multi-laboratory data comparisons at cross-over stations. The digital data are provided in several formats, including ASCII spreadsheet, Excel spreadsheet, netCDF, and Ocean Data View collection. In addition to the actual data values the IDP2014 also contains data quality flags and 1-σ data error values where available. Quality flags and error values are useful for data filtering. Metadata about data originators, analytical methods and original publications related to the data are linked to the data in an easily accessible way. The eGEOTRACES Electronic Atlas is the visual representation of the IDP2014 data providing section plots and a new kind of animated 3D scenes. The basin-wide 3D scenes allow for viewing of data from many cruises at the same time, thereby providing quick overviews of large-scale tracer distributions. In addition, the 3D scenes provide geographical and bathymetric context that is crucial for the interpretation and assessment of observed tracer plumes, as well as for making inferences about controlling processes.
    Description: We gratefully acknowledge financial support by the Scientific Committee on Oceanic Research (SCOR) through grants from the U.S. National Science Foundation, including grants OCE-0608600, OCE-0938349, and OCE-1243377. Financial support was also provided by the UK Natural Environment Research Council, the Ministry of Earth Science of India, the Centre National de Recherche Scientifique, l'Université Paul Sabatier de Toulouse, the Observatoire Midi-Pyrénées Toulouse, the Universitat Autònoma de Barcelona, the Kiel Excellence Cluster The Future Ocean, the Swedish Museum of Natural History, The University of Tokyo, The University of British Columbia, The Royal Netherlands Institute for Sea Research, the GEOMAR-Helmholtz Centre for Ocean Research Kiel, and the Alfred Wegener Institute.
    Keywords: GEOTRACES ; Trace elements ; Isotopes ; Electronic atlas
    Repository Name: Woods Hole Open Access Server
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    High-resolution water column survey to identify active sublacustrine hydrothermal discharge zones within Lake Rotomahana, North Island, New Zealand (2016)
    Elsevier
    Details
    Publication Date: 2022-05-26
    Description: This paper is not subject to U.S. copyright. The definitive version was published in Journal of Volcanology and Geothermal Research 314 (2016): 142-155, doi:10.1016/j.jvolgeores.2015.07.037.
    Description: Autonomous underwater vehicles were used to conduct a high-resolution water column survey of Lake Rotomahana using temperature, pH, turbidity, and oxidation–reduction potential (ORP) to identify active hydrothermal discharge zones within the lake. Five areas with active sublacustrine venting were identified: (1) the area of the historic Pink Terraces; (2) adjacent to the western shoreline subaerial “Steaming Cliffs,” boiling springs and geyser; (3) along the northern shoreline to the east of the Pink Terrace site; (4) the newly discovered Patiti hydrothermal system along the south margin of the 1886 Tarawera eruption rift zone; and (5) a location in the east basin (northeast of Patiti Island). The Pink Terrace hydrothermal system was active prior to the 1886 eruption of Mount Tarawera, but venting along the western shoreline, in the east basin, and the Patiti hydrothermal system appear to have been initiated in the aftermath of the eruption, similar to Waimangu Valley to the southwest. Different combinations of turbidity, pH anomalies (both positive and negative), and ORP responses suggest vent fluid compositions vary over short distances within the lake. The seasonal period of stratification limits vertical transport of heat to the surface layer and the hypolimnion temperature of Lake Rotomahana consequently increases with an average warming rate of ~ 0.010 °C/day due to both convective hydrothermal discharge and conductive geothermal heating. A sudden temperature increase occurred during our 2011 survey and was likely the response to an earthquake swarm just 11 days prior.
    Description: Funding was provided by GNS Strategic Development Fund.
    Keywords: Lake Rotomahana ; Hydrothermal venting ; pH ; Turbidity ; Oxidation–reduction potential ; Freshwater lakes
    Repository Name: Woods Hole Open Access Server
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    Triple oxygen isotopic composition of the high-3He/4He mantle (2016)
    Elsevier
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Geochimica et Cosmochimica Acta 176 (2016): 227–238, doi:10.1016/j.gca.2015.12.027.
    Description: Measurements of Xe isotope ratios in ocean island basalts (OIB) suggest that Earth’s mantle accreted heterogeneously, and that compositional remnants of accretion are sampled by modern, high-3He/4He OIB associated with the Icelandic and Samoan plumes. If so, the high-3He/4He source may also have a distinct oxygen isotopic composition from the rest of the mantle. Here, we test if the major elements of the high-3He/4He source preserve any evidence of heterogeneous accretion using measurements of three oxygen isotopes on olivine from a variety of high-3He/4He OIB locations. To high precision, the Δ17O value of high-3He/4He olivines from Hawaii, Pitcairn, Baffin Island and Samoa, are indistinguishable from bulk mantle olivine (Δ17OBulk Mantle − Δ17OHigh 3He/4He olivine = −0.002 ± 0.004 (2 × SEM)‰). Thus, there is no resolvable oxygen isotope evidence for heterogeneous accretion in the high-3He/4He source. Modelling of mixing processes indicates that if an early-forming, oxygen-isotope distinct mantle did exist, either the anomaly was extremely small, or the anomaly was homogenised away by later mantle convection. The δ18O values of olivine with the highest 3He/4He ratios from a variety of OIB locations have a relatively uniform composition (∼5‰). This composition is intermediate to values associated with the depleted MORB mantle and the average mantle. Similarly, δ18O values of olivine from high-3He/4He OIB correlate with radiogenic isotope ratios of He, Sr, and Nd. Combined, this suggests that magmatic oxygen is sourced from the same mantle as other, more incompatible elements and that the intermediate δ18O value is a feature of the high-3He/4He mantle source. The processes responsible for the δ18O signature of high-3He/4He mantle are not certain, but δ18O–87Sr/86Sr correlations indicate that it may be connected to a predominance of a HIMU-like (high U/Pb) component or other moderate δ18O components recycled into the high-3He/4He source.
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    The origin of vertebrate gills (2017)
    Elsevier
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Current Biology 27 (2017): 729-732, doi:10.1016/j.cub.2017.01.022.
    Description: Pharyngeal gills are a fundamental feature of the vertebrate body plan. However, the evolutionary history of vertebrate gills has been the subject of a long-standing controversy. It is thought that gills evolved independently in cyclostomes (jawless vertebrates—lampreys and hagfish) and gnathostomes (jawed vertebrates—cartilaginous and bony fishes), based on their distinct embryonic origins: the gills of cyclostomes derive from endoderm, while gnathostome gills were classically thought to derive from ectoderm. Here, we demonstrate by cell lineage tracing that the gills of a cartilaginous fish, the little skate (Leucoraja erinacea), are in fact endodermally derived. This finding supports the homology of gills in cyclostomes and gnathostomes, and a single origin of pharyngeal gills prior to the divergence of these two ancient vertebrate lineages.
    Description: This research was supported by a Royal Society University Research Fellowship ( UF130182 ) and a grant from the University of Cambridge Isaac Newton Trust ( 14.23z ) to J.A.G. O.R.A.T. was supported by the Wellcome Trust (PhD studentship 109147/Z/15/Z) and the Cambridge Commonwealth Trust.
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    Corrigendum to “Insights into methane dynamics from analysis of authigenic carbonates and chemosynthetic mussels at newly-discovered Atlantic Margin seeps” [Earth Planet. Sci. Lett. 449 (2016) 332–344] (2017)
    Elsevier
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    Publication Date: 2022-05-26
    Description: This paper is not subject to U.S. copyright. The definitive version was published in Earth and Planetary Science Letters 475 (2017): 268, doi:10.1016/j.epsl.2017.07.037.
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    Observations and 3D hydrodynamics-based modeling of decadal-scale shoreline change along the Outer Banks, North Carolina (2017)
    Elsevier
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    Publication Date: 2022-05-26
    Description: This paper is not subject to U.S. copyright. The definitive version was published in Coastal Engineering 120 (2017): 78-92, doi:10.1016/j.coastaleng.2016.11.014.
    Description: Long-term decadal-scale shoreline change is an important parameter for quantifying the stability of coastal systems. The decadal-scale coastal change is controlled by processes that occur on short time scales (such as storms) and long-term processes (such as prevailing waves). The ability to predict decadal-scale shoreline change is not well established and the fundamental physical processes controlling this change are not well understood. Here we investigate the processes that create large-scale long-term shoreline change along the Outer Banks of North Carolina, an uninterrupted 60 km stretch of coastline, using both observations and a numerical modeling approach. Shoreline positions for a 24-yr period were derived from aerial photographs of the Outer Banks. Analysis of the shoreline position data showed that, although variable, the shoreline eroded an average of 1.5 m/yr throughout this period. The modeling approach uses a three-dimensional hydrodynamics-based numerical model coupled to a spectral wave model and simulates the full 24-yr time period on a spatial grid running on a short (second scale) time-step to compute the sediment transport patterns. The observations and the model results show similar magnitudes (O(105 m3/yr)) and patterns of alongshore sediment fluxes. Both the observed and the modeled alongshore sediment transport rates have more rapid changes at the north of our section due to continuously curving coastline, and possible effects of alongshore variations in shelf bathymetry. The southern section with a relatively uniform orientation, on the other hand, has less rapid transport rate changes. Alongshore gradients of the modeled sediment fluxes are translated into shoreline change rates that have agreement in some locations but vary in others. Differences between observations and model results are potentially influenced by geologic framework processes not included in the model. Both the observations and the model results show higher rates of erosion (∼−1 m/yr) averaged over the northern half of the section as compared to the southern half where the observed and modeled averaged net shoreline changes are smaller (〈0.1 m/yr). The model indicates accretion in some shallow embayments, whereas observations indicate erosion in these locations. Further analysis identifies that the magnitude of net alongshore sediment transport is strongly dominated by events associated with high wave energy. However, both big- and small- wave events cause shoreline change of the same order of magnitude because it is the gradients in transport, not the magnitude, that are controlling shoreline change. Results also indicate that alongshore momentum is not a simple balance between wave breaking and bottom stress, but also includes processes of horizontal vortex force, horizontal advection and pressure gradient that contribute to long-term alongshore sediment transport. As a comparison to a more simple approach, an empirical formulation for alongshore sediment transport is used. The empirical estimates capture the effect of the breaking term in the hydrodynamics-based model, however, other processes that are accounted for in the hydrodynamics-based model improve the agreement with the observed alongshore sediment transport.
    Description: This study was also supported by the United States Geological Survey Coastal Change Processes Project and Department of the Interior Hurricane Sandy Recovery program.
    Keywords: Sediment transport ; Shoreline change ; Alongshore transport ; Outer Banks; NC ; Aerial photography ; COAWST ; ROMS ; SWAN ; Three-dimensional ; Modeling ; Wave modeling ; Nearshore modeling ; Model coupling
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    Target detection in insects : optical, neural and behavioral optimizations (2017)
    Elsevier
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Current Opinion in Neurobiology 41 (2016): 122–128, doi:10.1016/j.conb.2016.09.001.
    Description: Motion vision provides important cues for many tasks. Flying insects, for example, may pursue small, fast moving targets for mating or feeding purposes, even when these are detected against self-generated optic flow. Since insects are small, with size-constrained eyes and brains, they have evolved to optimize their optical, neural and behavioral target visualization solutions. Indeed, even if evolutionarily distant insects display different pursuit strategies, target neuron physiology is strikingly similar. Furthermore, the coarse spatial resolution of the insect compound eye might actually be beneficial when it comes to detection of moving targets. In conclusion, tiny insects show higher than expected performance in target visualization tasks.
    Description: AFOSR for funding to PGB and KN (FA9550-15-1-0188).
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    An optimized method for cryogenic storage of Xenopus sperm to maximise the effectiveness of research using genetically altered frogs (2017)
    Elsevier
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Theriogenology 92 (2017): 149–155, doi:10.1016/j.theriogenology.2017.01.007.
    Description: Cryogenic storage of sperm from genetically altered Xenopus improves cost effectiveness and animal welfare associated with their use in research; currently it is routine for X. tropicalis but not reliable for X. laevis. Here we compare directly the three published protocols for Xenopus sperm freeze-thaw and determine whether sperm storage temperature, method of testes maceration and delays in the freezing protocols affect successful fertilisation and embryo development in X. laevis. We conclude that the protocol is robust and that the variability observed in fertilisation rates is due to differences between individuals. We show that the embryos made from the frozen-thawed sperm are normal and that the adults they develop into are reproductively indistinguishable from others in the colony. This opens the way for using cryopreserved sperm to distribute dominant genetically altered (GA) lines, potentially saving travel-induced stress to the male frogs, reducing their numbers used and making Xenopus experiments more cost effective.
    Description: The EXRC is supported by the Wellcome Trust (101480/Z), BBSRC (BB/K019988/1) and NC3Rs (NC/P001009/1). The NXR is supported by a grant from the NIH (P40 OD010997).
    Keywords: Xenopus ; Sperm ; Cryopreservation ; Stock centres ; Genetically altered lines ; 3Rs
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    Perspectives on Chemical Oceanography in the 21st century : participants of the COME ABOARD Meeting examine aspects of the field in the context of 40 years of DISCO (2017)
    Elsevier
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marine Chemistry 196 (2017): 181-190, doi:10.1016/j.marchem.2017.09.002.
    Description: The questions that chemical oceanographers prioritize over the coming decades, and the methods we use to address these questions, will define our field's contribution to 21st century science. In recognition of this, the U.S. National Science Foundation and National Oceanic and Atmospheric Administration galvanized a community effort (the Chemical Oceanography MEeting: A BOttom-up Approach to Research Directions, or COME ABOARD) to synthesize bottom-up perspectives on selected areas of research in Chemical Oceanography. Representing only a small subset of the community, COME ABOARD participants did not attempt to identify targeted research directions for the field. Instead, we focused on how best to foster diverse research in Chemical Oceanography, placing emphasis on the following themes: strengthening our core chemical skillset; expanding our tools through collaboration with chemists, engineers, and computer scientists; considering new roles for large programs; enhancing interface research through interdisciplinary collaboration; and expanding ocean literacy by engaging with the public. For each theme, COME ABOARD participants reflected on the present state of Chemical Oceanography, where the community hopes to go and why, and actionable pathways to get there. A unifying concept among the discussions was that dissimilar funding structures and metrics of success may be required to accommodate the various levels of readiness and stages of knowledge development found throughout our community. In addition to the science, participants of the concurrent Dissertations Symposium in Chemical Oceanography (DISCO) XXV, a meeting of recent and forthcoming Ph.D. graduates in Chemical Oceanography, provided perspectives on how our field could show leadership in addressing long-standing diversity and early-career challenges that are pervasive throughout science. Here we summarize the COME ABOARD Meeting discussions, providing a synthesis of reflections and perspectives on the field.
    Description: The authors thank, NSFNSF-OCE-1356972, NSF-OCE-1737724, and NOAANA16NMF4320058 for initiating and funding the COME ABOARD Meeting in concert with DISCO XXV to promote a bottom-up approach to research directions.
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    Emerging trends in the sea state of the Beaufort and Chukchi seas (2016)
    Elsevier
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ocean Modelling 105 (2016): 1-12, doi:10.1016/j.ocemod.2016.02.009
    Description: The sea state of the Beaufort and Chukchi seas is controlled by the wind forcing and the amount of ice-free water available to generate surface waves. Clear trends in the annual duration of the open water season and in the extent of the seasonal sea ice minimum suggest that the sea state should be increasing, independent of changes in the wind forcing. Wave model hindcasts from four selected years spanning recent conditions are consistent with this expectation. In particular, larger waves are more common in years with less summer sea ice and/or a longer open water season, and peak wave periods are generally longer. The increase in wave energy may affect both the coastal zones and the remaining summer ice pack, as well as delay the autumn ice-edge advance. However, trends in the amount of wave energy impinging on the ice-edge are inconclusive, and the associated processes, especially in the autumn period of new ice formation, have yet to be well-described by in situ observations. There is an implicit trend and evidence for increasing wave energy along the coast of northern Alaska, and this coastal signal is corroborated by satellite altimeter estimates of wave energy.
    Description: This work was supported by the Office of Naval Research, Code 322, “Arctic and Global Prediction”, directed by Drs. Martin Jeffries and Scott Harper. (Grant numbers and Principal Investigators are: Ackley, N000141310435; Babanin, N000141310278; Doble, N000141310290; Fairall, N0001413IP20046; Gemmrich, N000141310280; Girard-Ardhuin and Ardhuin, N000141612376; Graber, N000141310288; Guest, N0001413WX20830; Holt, N0001413IP20050; Lehner, N000141310303; Maksym, N000141310446; Perrie, N00014-15-1-2611; Rogers, N0001413WX20825; Shen, N000141310294; Squire, N000141310279; Stammerjohn, N000141310434; Thomson, N000141310284; Wadhams, N000141310289.)
    Keywords: Sea ice ; Arctic Ocean ; Ocean surface waves
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    Shelled pteropods in peril : assessing vulnerability in a high CO2 ocean (2017)
    Elsevier
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Earth-Science Reviews 169 (2017): 132–145, doi:10.1016/j.earscirev.2017.04.005.
    Description: The impact of anthropogenic ocean acidification (OA) on marine ecosystems is a vital concern facing marine scientists and managers of ocean resources. Euthecosomatous pteropods (holoplanktonic gastropods) represent an excellent sentinel for indicating exposure to anthropogenic OA because of the sensitivity of their aragonite shells to the OA conditions less favorable for calcification. However, an integration of observations, experiments and modelling efforts is needed to make accurate predictions of how these organisms will respond to future changes to their environment. Our understanding of the underlying organismal biology and life history is far from complete and must be improved if we are to comprehend fully the responses of these organisms to the multitude of stressors in their environment beyond OA. This review considers the present state of research and understanding of euthecosomatous pteropod biology and ecology of these organisms and considers promising new laboratory methods, advances in instrumentation (such as molecular, trace elements, stable isotopes, palaeobiology alongside autonomous sampling platforms, CT scanning and high-quality video recording) and novel field-based approaches (i.e. studies of upwelling and CO2 vent regions) that may allow us to improve our predictive capacity of their vulnerability and/or resilience. In addition to playing a critical ecological and biogeochemical role, pteropods can offer a significant value as an early-indicator of anthropogenic OA. This role as a sentinel species should be developed further to consolidate their potential use within marine environmental management policy making.
    Description: M.I. Berning is financed by the German Research Foundation Priority Programme 1158 Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas (Project DFG-1158 SCHR 667/15-1).
    Keywords: Euthecosomatous pteropods ; Ocean acidification ; Calcifying organisms ; Marine ecosystem ; Carbonate chemistry
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    Newly discovered deep-branching marine plastid lineages are numerically rare but globally distributed (2017)
    Elsevier
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Current Biology 27 (2017): R15–R16, doi:10.1016/j.cub.2016.11.032.
    Description: Ocean surface warming is resulting in an expansion of stratified, low-nutrient environments, a process referred to as ocean desertification. A challenge for assessing the impact of these changes is the lack of robust baseline information on the biological communities that carry out marine photosynthesis. Phytoplankton perform half of global biological CO2 uptake, fuel marine food chains, and include diverse eukaryotic algae that have photosynthetic organelles (plastids) acquired through multiple evolutionary events. While amassing data from ocean ecosystems for the Baselines Initiative (6,177 near full-length 16S rRNA gene sequences and 9.4 million high-quality 16S V1-V2 amplicons) we identified two deep-branching plastid lineages based on 16S rRNA gene data. The two lineages have global distributions, but do not correspond to known phytoplankton. How the newly discovered phytoplankton lineages contribute to food chains and vertical carbon export to the deep sea remains unknown, but their prevalence in expanding, low nutrient surface waters suggests they will have a role in future oceans.
    Description: This research was supported by ONR N000141310451 (A.M.), MBARI, GBMF 1668 and GBMF 3788 (A.Z.W.).
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    Tracking recurrence of correlation structure in neuronal recordings (2017)
    Elsevier
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Neuroscience Methods 275 (2017): 1-9, doi:10.1016/j.jneumeth.2016.10.009.
    Description: Correlated neuronal activity in the brain is hypothesized to contribute to information representation, and is important for gauging brain dynamics in health and disease. Due to high dimensional neural datasets, it is difficult to study temporal variations in correlation structure. We developed a multiscale method, Population Coordination (PCo), to assess neural population structure in multiunit single neuron ensemble and multi-site local field potential (LFP) recordings. PCo utilizes population correlation (PCorr) vectors, consisting of pair-wise correlations between neural elements. The PCo matrix contains the correlations between all PCorr vectors occurring at different times. We used PCo to interpret dynamics of two electrophysiological datasets: multisite LFP and single unit ensemble. In the LFP dataset from an animal model of medial temporal lobe epilepsy, PCo isolated anomalous brain states, where particular brain regions broke off from the rest of the brain's activity. In a dataset of rat hippocampal single-unit recordings, PCo enabled visualizing neuronal ensemble correlation structure changes associated with changes of animal environment (place-cell remapping). PCo allows directly visualizing high dimensional data. Dimensional reduction techniques could also be used to produce dynamical snippets that could be examined for recurrence. PCo allows intuitive, visual assessment of temporal recurrence in correlation structure directly in the high dimensionality dataset, allowing for immediate assessment of relevant dynamics at a single site. PCo can be used to investigate how neural correlation structure occurring at multiple temporal and spatial scales reflect underlying dynamical recurrence without intermediate reduction of dimensionality.
    Description: Supported by grants from the Simons Foundation (294388), and National Institutes of Health: R01EB022903; R01MH084038; R01MH099128; R01MH086638; R42NS064474; U01EB017695.
    Keywords: Correlation structure ; Temporal recurrence ; Multiscale analysis ; Neuronal ensembles
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    Clumped isotope composition of cold-water corals : a role for vital effects? (2016)
    Elsevier
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Geochimica et Cosmochimica Acta 179 (2016): 123-141, doi:10.1016/j.gca.2016.01.023.
    Description: The carbonate clumped isotope thermometer is a promising tool for determining past ocean temperatures. It is based on the temperature dependence of rare isotopes ‘clumping’ into the same carbonate ion group in the carbonate mineral lattice. The extent of this clumping effect is independent of the isotope composition of the water from which carbonate precipitates, providing unique advantages over many other paleotemperature proxies. Existing calibrations of this thermometer in cold-water and warm-water corals suggest clumped isotope ‘vital effects’ are negligible in cold-water corals but may be significant in warm-water corals. Here, we test the calibration of the carbonate clumped isotope thermometer in cold-water corals with a recently collected and well characterised sample set spanning a range of coral genera (Balanophyllia, Caryophyllia, Dasmosmilia, Desmophyllum, Enallopsammia and Javania). The clumped isotope compositions (Δ47) of these corals exhibit systematic dependences on their growth temperatures, confirming the basis of the carbonate clumped isotope thermometer. However, some cold-water coral genera show Δ47 values that are higher than the expected equilibrium values by up to 0.05‰ (equivalent to underestimating temperature by ∼9 °C) similar to previous findings for some warm-water corals. This finding suggests that the vital effects affecting corals Δ47 are common to both warm- and cold-water corals. By comparison with models of the coral calcification process we suggest that the clumped isotope offsets in these genera are related to the kinetic isotope effects associated with CO2 hydration/hydroxylation reactions in the corals’ calcifying fluid. Our findings complicate the use of the carbonate clumped isotope thermometer in corals, but suggest that species- or genus-specific calibrations could be useful for the future application of this paleotemperature proxy.
    Description: This work was supported by a British National Environment Research Council studentship to P. Spooner (NE/K500823/1), National Science Foundation Grant NSF-ANT-1246387 and The Penzance Endowed Fund in Support of Assistant Scientists (WHOI) to W. Guo, and by funds from the European Research Council, the Leverhulme Trust and a Marie Curie Reintegration grant.
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