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  • Elsevier  (15)
  • European Geosciences Union  (7)
  • 2020-2023  (22)
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  • 1
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    Ideas and perspectives: a strategic assessment of methane and nitrous oxide measurements in the marine environment (2021)
    European Geosciences Union
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    Publikationsdatum: 2022-05-26
    Beschreibung: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Wilson, S. T., Al-Haj, A. N., Bourbonnais, A., Frey, C., Fulweiler, R. W., Kessler, J. D., Marchant, H. K., Milucka, J., Ray, N. E., Suntharalingam, P., Thornton, B. F., Upstill-Goddard, R. C., Weber, T. S., Arevalo-Martinez, D. L., Bange, H. W., Benway, H. M., Bianchi, D., Borges, A., V., Chang, B. X., Crill, P. M., del Valle, D. A., Farias, L., Joye, S. B., Kock, A., Labidi, J., Manning, C. C., Pohlman, J. W., Rehder, G., Sparrow, K. J., Tortell, P. D., Treude, T., Valentine, D. L., Ward, B. B., Yang, S., & Yurganov, L. N. Ideas and perspectives: a strategic assessment of methane and nitrous oxide measurements in the marine environment. Biogeosciences, 17(22), (2020): 5809-5828, https://doi.org/10.5194/bg-17-5809-2020.
    Beschreibung: In the current era of rapid climate change, accurate characterization of climate-relevant gas dynamics – namely production, consumption, and net emissions – is required for all biomes, especially those ecosystems most susceptible to the impact of change. Marine environments include regions that act as net sources or sinks for numerous climate-active trace gases including methane (CH4) and nitrous oxide (N2O). The temporal and spatial distributions of CH4 and N2O are controlled by the interaction of complex biogeochemical and physical processes. To evaluate and quantify how these mechanisms affect marine CH4 and N2O cycling requires a combination of traditional scientific disciplines including oceanography, microbiology, and numerical modeling. Fundamental to these efforts is ensuring that the datasets produced by independent scientists are comparable and interoperable. Equally critical is transparent communication within the research community about the technical improvements required to increase our collective understanding of marine CH4 and N2O. A workshop sponsored by Ocean Carbon and Biogeochemistry (OCB) was organized to enhance dialogue and collaborations pertaining to marine CH4 and N2O. Here, we summarize the outcomes from the workshop to describe the challenges and opportunities for near-future CH4 and N2O research in the marine environment.
    Beschreibung: This article was an outcome of a workshop organized by the Ocean Carbon and Biogeochemistry (OCB) project office, which is supported by the US National Science Foundation (grant no. 1558412) and the National Aeronautics and Space Administration (grant no. NNX17AB17G). The workshop received additional funding from the Scientific Committee on Ocean Research (SCOR) which receives funding from the US National Science Foundation (grant no. 1840868) and contributions by additional national SCOR committees. The Chilean COPAS N2O time-series measurements were supported by Agencia Nacional de Investigación y Desarrollo (grant no. 1200861).
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  • 2
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    Geochemical zones and environmental gradients for soils from the central Transantarctic Mountains, Antarctica (2021)
    European Geosciences Union
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    Publikationsdatum: 2022-05-27
    Beschreibung: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Diaz, M. A., Gardner, C. B., Welch, S. A., Jackson, W. A., Adams, B. J., Wall, D. H., Hogg, I. D., Fierer, N., & Lyons, W. B. Geochemical zones and environmental gradients for soils from the central Transantarctic Mountains, Antarctica. Biogeosciences, 18(5), (2021): 1629-1644. https://doi.org/10.5194/bg-18-1629-2021.
    Beschreibung: Previous studies have established links between biodiversity and soil geochemistry in the McMurdo Dry Valleys, Antarctica, where environmental gradients are important determinants of soil biodiversity. However, these gradients are not well established in the central Transantarctic Mountains, which are thought to represent some of the least hospitable Antarctic soils. We analyzed 220 samples from 11 ice-free areas along the Shackleton Glacier (∼ 85∘ S), a major outlet glacier of the East Antarctic Ice Sheet. We established three zones of distinct geochemical gradients near the head of the glacier (upper), its central part (middle), and at the mouth (lower). The upper zone had the highest water-soluble salt concentrations with total salt concentrations exceeding 80 000 µg g−1, while the lower zone had the lowest water-soluble N:P ratios, suggesting that, in addition to other parameters (such as proximity to water and/or ice), the lower zone likely represents the most favorable ecological habitats. Given the strong dependence of geochemistry on geographic parameters, we developed multiple linear regression and random forest models to predict soil geochemical trends given latitude, longitude, elevation, distance from the coast, distance from the glacier, and soil moisture (variables which can be inferred from remote measurements). Confidence in our random forest model predictions was moderately high with R2 values for total water-soluble salts, water-soluble N:P, ClO−4, and ClO−3 of 0.81, 0.88, 0.78, and 0.74, respectively. These modeling results can be used to predict geochemical gradients and estimate salt concentrations for other Transantarctic Mountain soils, information that can ultimately be used to better predict distributions of soil biota in this remote region.
    Beschreibung: This research has been supported by the National Science Foundation (grant nos. OPP 1341631, GRFP 60041697, OPP 1341618, OPP 1341629, and OPP 1341736).
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  • 3
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    Assessing the potential capability of reconstructing glacial Atlantic water masses and AMOC using multiple proxies in CESM (2020)
    Elsevier
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    Publikationsdatum: 2022-10-26
    Beschreibung: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Gu, S., Liu, Z., Oppo, D. W., Lynch-Stieglitz, J., Jahn, A., Zhang, J., & Wu, L. Assessing the potential capability of reconstructing glacial Atlantic water masses and AMOC using multiple proxies in CESM. Earth and Planetary Science Letters, 541, (2020): 11629, doi:10.1016/j.epsl.2020.116294.
    Beschreibung: Reconstructing the Atlantic Meridional Overturning Circulation (AMOC) during the Last Glacial Maximum (LGM) is essential for understanding glacial-interglacial climate change and the carbon cycle. However, despite many previous studies, uncertainties remain regarding the glacial water mass distributions in the Atlantic and the AMOC intensity. Here we use an isotope enabled ocean model with multiple geotracers (δ 13 C,E Νd,231 Pa/ 230Th,δ 18 Ο and Δ 14 C) and idealized water tracers to study the potential constraints on LGM ocean circulation from multiple proxies. Our model suggests that the glacial Atlantic water mass distribution can be accurately constrained by the air-sea gas exchange signature of water masses (δ13 C AS), but E Nd might overestimate the North Atlantic Deep Water (NADW) percentage in the deep Atlantic probably because of the boundary source of Nd. A sensitivity experiment with an AMOC of similar geometry but much weaker strength suggests that the correct AMOC geometry is more important than the AMOC strength for simulating the observed glacial δ13 C AS and E Nd and distributions. The kinematic tracer 231Pa/230Th is sensitive to AMOC intensity, but the interpretation might be complicated by the AMOC geometry and AABW transport changes during the LGM. δ 18 Ο in the benthic foraminifera (δ 18 Οc) from the Florida Straits provides a consistent measure of the upper ocean boundary current in the model, which potentially provides an unambiguous method to reconstruct glacial AMOC intensity. Finally, we propose that the moderate difference between AMOC intensity at LGM and PD, if any, is caused by the competition of the responses to CO2 forcing and continental ice sheet forcing.
    Beschreibung: We thank two anonymous reviewers for their useful and constructive comments. We also thank Editor Dr Laura F. Robinson for handling the manuscript. This work is supported by National Science Foundation of China No. 41630527, US National Science Foundation (NSF) P2C2 projects (1401778, 1401802, and 1566432). We would like to acknowledge the high-performance computing support from Yellowstone (ark:/85065/d7wd3xhc) and Cheyenne (doi:10.5065/D6RX99HX) provided by NCAR's Computational and Information Systems Laboratory, sponsored by the National Science Foundation and from Center for High Performance Computing and System Simulation, Pilot National Laboratory for Marine Science and Technology (Qingdao). Data used to produce the results in this study can be obtained from HPSS at CISL: /home/sgu28/CTRACE_decadal or by contacting the authors.
    Schlagwort(e): Last Glacial Maximum ; AMOC ; Water mass ; Multi-proxy
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  • 4
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    Linking diatom-diazotroph symbioses to nitrogen cycle perturbations and deep-water anoxia: insights from Mediterranean sapropel events (2021)
    Elsevier
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    Publikationsdatum: 2022-10-26
    Beschreibung: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Elling, F. J., Hemingway, J. D., Kharbush, J. J., Becker, K. W., Polik, C. A., & Pearson, A. Linking diatom-diazotroph symbioses to nitrogen cycle perturbations and deep-water anoxia: insights from Mediterranean sapropel events. Earth and Planetary Science Letters, 571, (2021): 117110, https://doi.org/10.1016/j.epsl.2021.117110.
    Beschreibung: Elevated organic matter (OM) export flux promotes marine anoxia, thus increasing carbon sequestration efficiency and decreasing atmospheric carbon dioxide levels. However, the mechanisms that trigger and sustain anoxic events—particularly those associated with nutrient-poor, oligotrophic surface waters—remain poorly constrained. Mediterranean Sea sapropels are well-preserved sediments deposited during episodic anoxic events throughout the Plio-Pleistocene; as such, they may provide unique insight into the biogeochemical and ecological drivers of—and responses to—marine anoxia. Using biomarker distributions, we demonstrate that anaerobic ammonium oxidizing (anammox) bacteria and diazotrophic endosymbionts of mat- and/or raft-forming diatoms were both abundant during sapropel events, particularly in the Ionian and Libyan seas. In these sapropels, the carbon isotope compositions of anammox biomarkers directly capture progressive 13C-depletion in deep-water dissolved inorganic carbon, indicating sustained carbon sequestration. To explain these observations, we propose a reinforcing feedback whereby initial nutrient and/or circulation perturbations promote fixed nitrogen loss via intensified anammox and heterotrophic denitrification, which in turn favors proliferation of rapidly sinking diatom-diazotroph symbiotic consortia, increases OM burial flux, and sustains anoxia. This mechanism resolves the long-standing conundrum that small and buoyant diazotrophs are apparently associated with high OM export during periods of marine anoxia and oligotrophy.
    Beschreibung: This work was funded through the Gordon and Betty Moore Foundation and US National Science Foundation grants 1843285, 1702262 and 1349126 (to A.P.). Additional financial support was provided by the Postdoctoral Program at the Woods Hole Oceanographic Institution and U.S. Geological Survey (K.W.B.).
    Schlagwort(e): Nammox ; Anoxia ; Compound-specific, δ13, C ; Diatom-diazotroph symbioses ; N2-fixation ; Mediterranean sapropels
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  • 5
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    Unprecedented summer hypoxia in southern Cape Cod Bay: an ecological response to regional climate change? (2022)
    European Geosciences Union
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    Publikationsdatum: 2022-12-22
    Beschreibung: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scully, M. E., Geyer, W. R., Borkman, D., Pugh, T. L., Costa, A., & Nichols, O. C. Unprecedented summer hypoxia in southern Cape Cod Bay: an ecological response to regional climate change? Biogeosciences, 19(14), (2022): 3523–3536, https://doi.org/10.5194/bg-19-3523-2022.
    Beschreibung: In late summer 2019 and 2020 bottom waters in southern Cape Cod Bay (CCB) became depleted of dissolved oxygen (DO), with documented benthic mortality in both years. Hypoxic conditions formed in relatively shallow water where the strong seasonal thermocline intersected the sea floor, both limiting vertical mixing and concentrating biological oxygen demand (BOD) over a very thin bottom boundary layer. In both 2019 and 2020, anomalously high sub-surface phytoplankton blooms were observed, and the biomass from these blooms provided the fuel to deplete sub-pycnocline waters of DO. The increased chlorophyll fluorescence was accompanied by a corresponding decrease in sub-pycnocline nutrients, suggesting that prior to 2019 physical conditions were unfavorable for the utilization of these deep nutrients by the late-summer phytoplankton community. It is hypothesized that significant alteration of physical conditions in CCB during late summer, which is the result of regional climate change, has favored the recent increase in sub-surface phytoplankton production. These changes include rapidly warming waters and significant shifts in summer wind direction, both of which impact the intensity and vertical distribution of thermal stratification and vertical mixing within the water column. These changes in water column structure are not only more susceptible to hypoxia but also have significant implications for phytoplankton dynamics, potentially allowing for intense late-summer blooms of Karenia mikimotoi, a species new to the area. K. mikimotoi had not been detected in CCB or adjacent waters prior to 2017; however, increasing cell densities have been reported in subsequent years, consistent with a rapidly changing ecosystem.
    Beschreibung: This research has been supported by the National Science Foundation (grant no. OCE-2053240) and the National Oceanic and Atmospheric Administration (grant no. NA20OAR4170506).
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  • 6
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    An evaluation of the C/N ratio of the mantle from natural CO2-rich gas analysis: Geochemical and cosmochemical implications (2020)
    Elsevier
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    Publikationsdatum: 2022-10-26
    Beschreibung: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marty, B., Almayrac, M., Barry, P. H., Bekaert, D., V., Broadley, M. W., Byrne, D. J., Ballentine, C. J., & Caracausi, A. An evaluation of the C/N ratio of the mantle from natural CO2-rich gas analysis: Geochemical and cosmochemical implications. Earth and Planetary Science Letters, 551, (2020): 116574, doi:10.1016/j.epsl.2020.116574.
    Beschreibung: The terrestrial carbon to nitrogen ratio is a key geochemical parameter that can provide information on the nature of Earth's precursors, accretion/differentiation processes of our planet, as well as on the volatile budget of Earth. In principle, this ratio can be determined from the analysis of volatile elements trapped in mantle-derived rocks like mid-ocean ridge basalts (MORB), corrected for fractional degassing during eruption. However, this correction is critical and previous attempts have adopted different approaches which led to contrasting C/N estimates for the bulk silicate Earth (BSE) (Marty and Zimmermann, 1999; Bergin et al., 2015). Here we consider the analysis of CO2-rich gases worldwide for which a mantle origin has been determined using noble gas isotopes in order to evaluate the C/N ratio of the mantle source regions. These gases experienced little fractionation due to degassing, as indicated by radiogenic 4He / 40Ar* values (where 4He and 40Ar* are produced by the decay of U+Th, and 40K isotopes, respectively) close to the mantle production/accumulation values. The C/N and C/3 He ratios of gases investigated here are within the range of values previously observed in oceanic basalts. They point to an elevated mantle C/N ratio (∼350-470, molar) higher than those of potential cosmochemical accretionary endmembers. For example, the BSE C/N and 36 Ar / N ratios (160-220 and 75 x 10-7, respectively) are higher than those of CM-CI chondrites but within the range of CV-CO groups. This similarity suggests that the Earth accreted from evolved planetary precursors depleted in volatile and moderately volatile elements. Hence the high C / N composition of the BSE may be an inherited feature rather than the result of terrestrial differentiation. The C / N and 36 Ar / N ratios of the surface (atmosphere plus crust) and of the mantle cannot be easily linked to any known chondritic composition. However, these compositions are consistent with early sequestration of carbon into the mantle (but not N and noble gases), permitting the establishment of clement temperatures at the surface of our planet.
    Beschreibung: M.A, D.V.B, M.W.B, D.J.B and B.M were supported by the European Research Council (PHOTONIS project, grant agreement No. 695618 to B.M.). Samples were collected as part of Study # YELL-08056 - Xenon anomalies in the Yellowstone Hotspot. We would like to thank Annie Carlson and all of the rangers at the Yellowstone National Park for providing invaluable advice and help when collecting the samples. This work was partially supported by a grant (G-2016-7206) from the Alfred P. Sloan Foundation and the Deep Carbon Observatory to P.H.B as well as NSF award 2015789 to P.H.B.. Sampling at Mt. Etna and gas analysis was supported by Instituto Nazionale di Geofisica e Vulcanologia Palermo. Fruitful discussions with Marc Hirschmann helped us to shape the ideas presented in this work. We acknowledge detailed and insightful reviews by Sami Mikhail and an anonymous reviewer, and efficient editing by Frederic Moynier. This is CRPG contribution 2741.
    Schlagwort(e): Carbon ; Nitrogen ; Earth ; Mantle ; Gases
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  • 7
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    Water mass transformation in the Iceland Sea: contrasting two winters separated by four decades (2022)
    Elsevier
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    Publikationsdatum: 2022-10-11
    Beschreibung: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Våge, K., Semper, S., Valdimarsson, H., Jónsson, S., Pickart, R., & Moore, G. Water mass transformation in the Iceland Sea: contrasting two winters separated by four decades. Deep Sea Research Part I: Oceanographic Research Papers, 186, (2022): 103824, https://doi.org/10.1016/j.dsr.2022.103824.
    Beschreibung: Dense water masses formed in the Nordic Seas flow across the Greenland–Scotland Ridge and contribute substantially to the lower limb of the Atlantic Meridional Overturning Circulation. Originally considered an important source of dense water, the Iceland Sea gained renewed interest when the North Icelandic Jet — a current transporting dense water from the Iceland Sea into Denmark Strait — was discovered in the early 2000s. Here we use recent hydrographic data to quantify water mass transformation in the Iceland Sea and contrast the present conditions with measurements from hydrographic surveys conducted four decades earlier. We demonstrate that the large-scale hydrographic structure of the central Iceland Sea has changed significantly over this period and that the locally transformed water has become less dense, in concert with a retreating sea-ice edge and diminished ocean-to-atmosphere heat fluxes. This has reduced the available supply of dense water to the North Icelandic Jet, but also permitted densification of the East Greenland Current during its transit through the presently ice-free western Iceland Sea in winter. Together, these changes have significantly altered the contribution from the Iceland Sea to the overturning in the Nordic Seas over the four decade period.
    Beschreibung: Support for this work was provided by the Trond Mohn Foundation, Norway under grant BFS2016REK01 (K.V. and S.S.), the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 101022251 (S.S.), the US National Science Foundation under grants OCE-1259618 and OCE- 1948505 (R.S.P), and the Natural Sciences and Engineering Research Council of Canada (G.W.K.M).
    Schlagwort(e): Iceland Sea ; Water mass transformation ; North Icelandic Jet ; Iceland–Faroe Slope Jet ; East Greenland Current ; Denmark Strait overflow water
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  • 8
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    Remineralization dominating the δ13 C decrease in the mid-depth Atlantic during the last deglaciation (2021)
    Elsevier
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    Publikationsdatum: 2022-10-26
    Beschreibung: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Gu, S., Liu, Z., Oppo, D. W., Lynch-Stieglitz, J., Jahn, A., Zhang, J., Lindsay, K., & Wu, L. Remineralization dominating the δ13 C decrease in the mid-depth Atlantic during the last deglaciation. Earth and Planetary Science Letters, 571, (2021): 117106, https://doi.org/10.1016/j.epsl.2021.117106.
    Beschreibung: δ 13 C records from the mid-depth Atlantic show a pronounced decrease during the Heinrich Stadial 1 (HS1), a deglacial episode of dramatically weakened Atlantic Meridional Ocean Circulation (AMOC). Proposed explanations for this mid-depth decrease include a greater fraction of δ 13 C -depleted southern sourced water (SSW), a δ 13 C decrease in the North Atlantic Deep Water (NADW) end-member, and accumulation of the respired organic carbon. However, the relative importance of these proposed mechanisms cannot be quantitatively constrained from current available observations alone. Here we diagnose the individual contributions to the deglacial Atlantic mid-depth δ 13 C change from these mechanisms using a transient simulation with carbon isotopes and idealized tracers. We find that although the fraction of the low- δ 13 C SSW increases in response to a weaker AMOC during HS1, the water mass mixture change only plays a minor role in the mid-depth Atlantic δ 13 C decrease. Instead, increased remineralization due to the AMOC-induced mid-depth ocean ventilation decrease is the dominant cause. In this study, we differentiate between the deep end-members, which are assigned to deep water regions used in previous paleoceanography studies, and the surface end-members, which are from the near-surface water defined from the physical origin of deep water masses. We find that the deep NADW end-member includes additional remineralized material accumulated when sinking from the surface (surface NADW end-member). Therefore, the surface end-members should be used in diagnosing mechanisms of changes. Furthermore, our results suggest that remineralization in the surface end-member is more critical than the remineralization along the transport pathway from the near-surface formation region to the deep ocean, especially during the early deglaciation.
    Beschreibung: This work is supported by US National Science Foundation (NSF) P2C2 projects (1401778, 1401802, and 1566432), and the National Science Foundation of China No. 41630527. S.G. is supported by Shanghai Pujiang program.
    Schlagwort(e): δ13 C ; Water mass composition ; Remineralization ; End-member ; HS1
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  • 9
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    High precision noble gas measurements of hydrothermal quartz reveal variable loss rate of Xe from the Archean atmosphere (2022)
    Elsevier
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    Publikationsdatum: 2022-10-26
    Beschreibung: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Broadley, M., Byrne, D., Ardoin, L., Almayrac, M., Bekaert, D., & Marty, B. High precision noble gas measurements of hydrothermal quartz reveal variable loss rate of Xe from the Archean atmosphere. Earth and Planetary Science Letters, 588, (2022): 117577, https://doi.org/10.1016/j.epsl.2022.117577.
    Beschreibung: Determining the composition of the Archean atmosphere and oceans is vital to understanding the environmental conditions that existed on the surface of the early Earth. The analysis of atmospheric remnants in fluid inclusions trapped in Archean-aged samples has shown that the Xe isotopic signature of the Archean atmosphere progressively evolved via mass-dependent fractionation, arriving at a modern atmospheric composition around the Archean-Proterozoic transition. The mechanisms driving this evolution are however not well constrained, and it is not yet clear whether the evolution proceeded continuously or via episodic bursts. Providing further constraints on the evolution of Xe in the Archean atmosphere is hampered by the limited amounts of atmospheric gas trapped within fluid inclusions during mineral formation, which impacts the precision at which the Archean atmosphere can be determined. Here, we develop a new crush-and-accumulate extraction technique that enables the heavy noble gases (Ar, Kr and Xe) released from crushing large quantities of hydrothermal quartz to be accumulated and analysed to a higher precision than was previously possible. Using this new technique, we re-evaluate the composition of atmospheric gases trapped within fluid inclusions of 3.3 Ga quartz samples from Barberton, South Africa. We find that the Xe isotopic signature is fractionated by +10.3 ± 1.0‰u−1 (2 SE) relative to modern atmosphere, which is within uncertainty of, but slightly lower than, the previous determination of 12.9 ± 2.4‰u−1 for this sample (Avice et al., 2017). We show for the first time that the Kr/Xe ratio measured within Archean quartz samples is enriched in Xe compared to the modern atmosphere, demonstrating that the atmosphere has lost Xe since the Archean. This further reinforces the proposal of atmospheric escape as the primary mechanism for Earth's Xe loss. We further show that the atmospheric Kr/Xe and Xe isotope fractionation recorded in the Barberton quartz at 3.3 Ga is incompatible with a model describing atmospheric loss at a continuous rate under a constant fractionation factor. This gives credence to numerical models of hydrodynamic escape, which suggest that Xe was lost from the Archean atmosphere in episodic bursts rather than at a constant rate. Refining the evolution curve of atmospheric Xe isotopes using the new technique presented here has the potential to shed light on discrete atmospheric events that punctuated the evolution of the Archean Earth and accompanied the evolution of life.
    Beschreibung: This study was supported by the European Research Council (PHOTONIS project, grant agreement No. 695618). This is CRPG contribution #2820.
    Schlagwort(e): Archean atmosphere ; Noble gases ; Xenon ; Atmospheric escape
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  • 10
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    WAP-1D-VAR v1.0: development and evaluation of a one-dimensional variational data assimilation model for the marine ecosystem along the West Antarctic Peninsula (2021)
    European Geosciences Union
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    Publikationsdatum: 2022-05-27
    Beschreibung: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Kim, H. H., Luo, Y.-W., Ducklow, H. W., Schofield, O. M., Steinberg, D. K., & Doney, S. C. WAP-1D-VAR v1.0: development and evaluation of a one-dimensional variational data assimilation model for the marine ecosystem along the West Antarctic Peninsula. Geoscientific Model Development, 14(8), (2021): 4939–4975, https://doi.org/10.5194/gmd-14-4939-2021.
    Beschreibung: The West Antarctic Peninsula (WAP) is a rapidly warming region, with substantial ecological and biogeochemical responses to the observed change and variability for the past decades, revealed by multi-decadal observations from the Palmer Antarctica Long-Term Ecological Research (LTER) program. The wealth of these long-term observations provides an important resource for ecosystem modeling, but there has been a lack of focus on the development of numerical models that simulate time-evolving plankton dynamics over the austral growth season along the coastal WAP. Here, we introduce a one-dimensional variational data assimilation planktonic ecosystem model (i.e., the WAP-1D-VAR v1.0 model) equipped with a model parameter optimization scheme. We first demonstrate the modified and newly added model schemes to the pre-existing food web and biogeochemical components of the other ecosystem models that WAP-1D-VAR model was adapted from, including diagnostic sea-ice forcing and trophic interactions specific to the WAP region. We then present the results from model experiments where we assimilate 11 different data types from an example Palmer LTER growth season (October 2002–March 2003) directly related to corresponding model state variables and flows between these variables. The iterative data assimilation procedure reduces the misfits between observations and model results by 58 %, compared to before optimization, via an optimized set of 12 parameters out of a total of 72 free parameters. The optimized model results capture key WAP ecological features, such as blooms during seasonal sea-ice retreat, the lack of macronutrient limitation, and modeled variables and flows comparable to other studies in the WAP region, as well as several important ecosystem metrics. One exception is that the model slightly underestimates particle export flux, for which we discuss potential underlying reasons. The data assimilation scheme of the WAP-1D-VAR model enables the available observational data to constrain previously poorly understood processes, including the partitioning of primary production by different phytoplankton groups, the optimal chlorophyll-to-carbon ratio of the WAP phytoplankton community, and the partitioning of dissolved organic carbon pools with different lability. The WAP-1D-VAR model can be successfully employed to link the snapshots collected by the available data sets together to explain and understand the observed dynamics along the coastal WAP.
    Beschreibung: Hyewon Heather Kim and Scott C. Doney were supported by the National Aeronautics and Space Administration Ocean Biology and Biogeochemistry Program (grant no. NNX14AL86G) and the US National Science Foundation Office of Polar Programs (grant no. PLR-1440435 to Hugh W. Ducklow at Columbia University; Palmer LTER). Hyewon Heather Kim was additionally supported by the Investment in Science Fund and the Reuben F. and Elizabeth B. Richards Endowed Fund from Woods Hole Oceanographic Institution. Oscar M. Schofield and Deborah K. Steinberg were supported by US NSF grant no. PLR-1440435. Ya-Wei Luo was supported by National Natural Science Foundation of China project no. 41890802.
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Standort Signatur Erwartet Verfügbarkeit
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