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  • 11
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    The dynamic ocean biological pump: Insights from a global compilation of particulate organic carbon, CaCO3, and opal concentration profiles from the mesopelagic (2011)
    American Geophysical Union
    Details
    Publication Date: 2011-07-22
    Print ISSN: 0886-6236
    Electronic ISSN: 1944-9224
    Topics: Biology , Chemistry and Pharmacology , Geography , Geosciences , Physics
    Published by American Geophysical Union
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  • 12
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    Revisiting Carbon Flux Through the Ocean's Twilight Zone (2007)
    American Association for the Advancement of Science
    Details
    Publication Date: 2007-04-27
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science
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  • 13
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    The continental margin is a key source of iron to the HNLC North Pacific Ocean (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 35 (2008): L07608, doi:10.1029/2008GL033294.
    Description: Here we show that labile particulate iron and manganese concentrations in the upper 500 m of the Western Subarctic Pacific, an iron-limited High Nutrient Low Chlorophyll (HNLC) region, have prominent subsurface maxima between 100–200 m, reaching 3 nM and 600 pM, respectively. The subsurface concentration maxima in particulate Fe are characterized by a more reduced oxidation state, suggesting a source from primary volcagenic minerals such as from the Kuril/Kamchatka margin. The systematics of these profiles suggest a consistently strong lateral advection of labile Mn and Fe from redox-mobilized labile sources at the continental shelf supplemented by a more variable source of Fe from the upper continental slope. This subsurface supply of iron from the continental margin is shallow enough to be accessible to the surface through winter upwelling and vertical mixing, and is likely a key source of bioavailable Fe to the HNLC North Pacific.
    Description: Funding from the US Department of Energy, Office of Science, Biological and Environmental Research Program (JB) and WHOI Postdoctoral Scholars program, the Richard B. Sellars Endowed Research Fund, and the Andrew W. Mellon Foundation Endowed Fund for Innovative Research (PL).
    Keywords: Iron ; Continental margin ; HNLC
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 14
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    Revisiting carbon flux through the ocean's twilight zone (2010)
    American Association for the Advancement of Science
    Details
    Publication Date: 2017-01-04
    Description: Citation only. Published in Science 316: 567-570, doi: 10.1126/science.1137959
    Description: Funding was obtained primarily through the NSF, Ocean Sciences Programs in Chemical and Biological Oceanography, with additional support from the U.S. Department of Energy, Office of Science, Biological and Environmental Research Program, and other national programs, including the Australian Cooperative Research Centre program and Australian Antarctic Division.
    Keywords: Carbon flux ; Carbon sequestration ; Biological pump
    Repository Name: Woods Hole Open Access Server
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  • 15
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    Flux of particulate elements in the North Atlantic Ocean constrained by multiple radionuclides (2019)
    American Geophysical Union
    Details
    Publication Date: 2022-10-26
    Description: Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 32(12), (2019): 1738-1758, doi:10.1029/2018GB005994.
    Description: Sinking particles strongly regulate the distribution of reactive chemical substances in the ocean, including particulate organic carbon and other elements (e.g., P, Cd, Mn, Cu, Co, Fe, Al, and 232Th). Yet, the sinking fluxes of trace elements have not been well described in the global ocean. The U.S. GEOTRACES campaign in the North Atlantic (GA03) offers the first data set in which the sinking flux of carbon and trace elements can be derived using four different radionuclide pairs (238U:234Th ;210Pb:210Po; 228Ra:228Th; and 234U:230Th) at stations co‐located with sediment trap fluxes for comparison. Particulate organic carbon, particulate P, and particulate Cd fluxes all decrease sharply with depth below the euphotic zone. Particulate Mn, Cu, and Co flux profiles display mixed behavior, some cases reflecting biotic remineralization, and other cases showing increased flux with depth. The latter may be related to either lateral input of lithogenic material or increased scavenging onto particles. Lastly, particulate Fe fluxes resemble fluxes of Al and 232Th, which all have increasing flux with depth, indicating a dominance of lithogenic flux at depth by resuspended sediment transported laterally to the study site. In comparing flux estimates derived using different isotope pairs, differences result from different timescales of integration and particle size fractionation effects. The range in flux estimates produced by different methods provides a robust constraint on the true removal fluxes, taking into consideration the independent uncertainties associated with each method. These estimates will be valuable targets for biogeochemical modeling and may also offer insight into particle sinking processes.
    Description: This study grew out of a synthesis workshop at the Lamont‐Doherty Earth Observatory of Columbia University in August 2016. This workshop was sponsored by the U.S. GEOTRACES Project Office (NSF 1536294) and the Ocean Carbon and Biogeochemistry (OCP) Project Office (NSF 1558412 and NASA NNX17AB17G). The U.S. National Science Foundation supported all of the analytical work on GA03. Kuanbo Zhou measured 228Th in the large size class particles (NSF 0925158 to WHOI). NSF 1061128 to Stony Brook University supported the BaRFlux project, for which Chistina Heilbrun is acknowledged for laboratory and field work. The lead author acknowledges support from a start‐up grant from the University of Southern Mississippi. Two anonymous reviewers are thanked for their constructive comments. All GEOTRACES GA03 data used in this study are accessible through the Biological and Chemical Oceanography Data Management Office (http://data.bco‐dmo.org/jg/dir/BCO/GEOTRACES/NorthAtlanticTransect/), and derived parameters are reported in the supporting information.
    Description: 2019-05-22
    Keywords: Biological carbon pump ; Trace metals ; North Atlantic ; Export ; GEOTRACES
    Repository Name: Woods Hole Open Access Server
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  • 16
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    Ironing out Fe residence time in the dynamic upper ocean (2020)
    American Geophysical Union
    Details
    Publication Date: 2022-10-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Black, E. E., Kienast, S. S., Lemaitre, N., Lam, P. J., Anderson, R. F., Planquette, H., Planchon, F., & Buesseler, K. O. Ironing out Fe residence time in the dynamic upper ocean. Global Biogeochemical Cycles, 34(9), (2020): e2020GB006592, doi:10.1029/2020GB006592.
    Description: Although iron availability has been shown to limit ocean productivity and influence marine carbon cycling, the rates of processes driving iron's removal and retention in the upper ocean are poorly constrained. Using 234Th‐ and sediment‐trap data, most of which were collected through international GEOTRACES efforts, we perform an unprecedented observation‐based assessment of iron export from and residence time in the upper ocean. The majority of these new residence time estimates for total iron in the surface ocean (0–250 m) fall between 10 and 100 days. The upper ocean residence time of dissolved iron, on the other hand, varies and cycles on sub‐annual to annual timescales. Collectively, these residence times are shorter than previously thought, and the rates and timescales presented here will contribute to ongoing efforts to integrate iron into global biogeochemical models predicting climate and carbon dioxide sequestration in the ocean in the 21st century and beyond.
    Description: We would like to thank S. Albani for providing the dust model results (Community Atmosphere Model, C4fn) and the three anonymous reviewers for their constructive comments. The U.S. GEOTRACES work was supported by the National Science Foundation (OCE‐1232669 and OCE‐1518110) and E. Black was also funded by a NASA Earth and Space Science Graduate Fellowship (NNX13AP31H) and the Ocean Frontier Institute. The GEOVIDE work was funded by the Flanders Research Foundation (G071512N), the Vrije Universiteit Brussel (SRP‐2), the French ANR Blanc GEOVIDE (ANR‐13‐BS06‐0014), ANR RPDOC BITMAP (ANR‐12‐PDOC‐0025‐01), IFREMER, CNRS‐INSU (programme LEFE), INSU OPTIMISP, and Labex‐Mer (ANR‐10‐LABX‐19).
    Keywords: Thorium‐234 ; Iron ; Export ; GEOTRACES ; Residence time
    Repository Name: Woods Hole Open Access Server
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  • 17
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    Dissolved and particulate barium distributions along the US GEOTRACES North Atlantic and East Pacific zonal transects (GA03 and GP16): global implications for the marine barium cycle (2022)
    American Geophysical Union
    Details
    Publication Date: 2022-10-26
    Description: Author Posting. © American Geophysical Union, 2022. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 36(6), (2022): e2022GB007330, https://doi.org/10.1029/2022gb007330.
    Description: Processes controlling dissolved barium (dBa) were investigated along the GEOTRACES GA03 North Atlantic and GP16 Eastern Tropical Pacific transects, which traversed similar physical and biogeochemical provinces. Dissolved Ba concentrations are lowest in surface waters (∼35–50 nmol kg−1) and increase to 70–80 and 140–150 nmol kg−1 in deep waters of the Atlantic and Pacific transects, respectively. Using water mass mixing models, we estimate conservative mixing that accounts for most of dBa variability in both transects. To examine nonconservative processes, particulate excess Ba (pBaxs) formation and dissolution rates were tracked by normalizing particulate excess 230Th activities. Th-normalized pBaxs fluxes, with barite as the likely phase, have subsurface maxima in the top 1,000 m (∼100–200 μmol m−2 year−1 average) in both basins. Barite precipitation depletes dBa within oxygen minimum zones from concentrations predicted by water mass mixing, whereas inputs from continental margins, particle dissolution in the water column, and benthic diffusive flux raise dBa above predications. Average pBaxs burial efficiencies along GA03 and GP16 are ∼37% and 17%–100%, respectively, and do not seem to be predicated on barite saturation indices in the overlying water column. Using published values, we reevaluate the global freshwater dBa river input as 6.6 ± 3.9 Gmol year−1. Estuarine mixing processes may add another 3–13 Gmol year−1. Dissolved Ba inputs from broad shallow continental margins, previously unaccounted for in global marine summaries, are substantial (∼17 Gmol year−1), exceeding terrestrial freshwater inputs. Revising river and shelf dBa inputs may help bring the marine Ba isotope budget more into balance.
    Description: The International GEOTRACES Programme is possible in part thanks to the support from the U.S. National Science Foundation (Grant OCE-1840868) to the Scientific Committee on Oceanic Research (SCOR). This research was supported by the National Science Foundation under Grant No. NSF OCE-0927951, NSF OCE-1137851, NSF OCE-1261214, and NSF OCE-1925503 to A. M. Shiller; NSF OCE-1829563 to R. F. Anderson; NSF OCE-0927064 and NSF OCE-1233688 to R. F. Anderson and M. Q. Fleisher; NSF OCE-0927754 to R. Lawrence Edwards; NSF OCE-1233903 to R. Lawrence Edwards and H. Cheng; NSF OCE-0926860 to L. F. Robinson; NSF OCE-0963026 and NSF OCE-1518110 to P. J. Lam; and NSF OCE-1232814 to B. S. Twining.
    Keywords: Barium ; Excess barium ; Barite ; GEOTRACES ; Th-normalized flux ; Burial efficiency
    Repository Name: Woods Hole Open Access Server
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  • 18
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    Insights from the U-238-th-234 method into the coupling of biological export and the cycling of cadmium, cobalt, and manganese in the southeast Pacific Ocean (2019)
    American Geophysical Union
    Details
    Publication Date: 2022-10-26
    Description: Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 33(1), (2019): 15-36, doi:10.1029/2018GB005985.
    Description: Better constraints on the magnitude of particulate export and the residence times of trace elements are required to understand marine food web dynamics, track the transport of anthropogenic trace metals in the ocean, and improve global climate models. While prior studies have been successful in constructing basin‐scale budgets of elements like carbon in the upper ocean, the cycling of particulate trace metals is poorly understood. The 238U‐234Th method is used here with data from the GP‐16 GEOTRACES transect to investigate the upper ocean processes controlling the particulate export of cadmium, cobalt, and manganese in the southeastern Pacific. Patterns in the flux data indicated that particulate cadmium and cobalt behave similarly to particulate phosphorus and organic carbon, with the highest export in the productive coastal region and decreasing flux with depth due to remineralization. The export of manganese was influenced by redox conditions at the low oxygen coastal stations and by precipitation and/or scavenging elsewhere. Residence times with respect to export (total inventory divided by particulate flux) for phosphorus, cadmium, cobalt, and manganese in the upper 100 and 200 m were determined to be on the order of months to years. These GEOTRACES‐based synthesis efforts, combining a host of concentration and tracer data with unprecedented resolution, will help to close the oceanic budgets of trace metals.
    Description: This work was supported by the National Science Foundation (OCE‐1232669 and OCE‐1518110), and Erin Black was also funded by a NASA Earth and Space Science Graduate Fellowship (NNX13AP31H). The authors would like to thank the captain, crew, and scientists aboard the R/V Thomas G. Thompson. A special thanks to two anonymous reviewers and Virginie Sanial for providing the additional 228Ra‐based estimates for Cd. All original data have been made available in either the supporting information or through BCO‐DMO (see Website and Database References).
    Description: 2019-06-10
    Keywords: Tthorium ; Export ; Trace metals ; Residence time
    Repository Name: Woods Hole Open Access Server
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  • 19
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    Strong margin influence on the Arctic Ocean Barium Cycle revealed by pan‐Arctic synthesis (2022)
    American Geophysical Union
    Details
    Publication Date: 2022-10-26
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Whitmore, L., Shiller, A., Horner, T., Xiang, Y., Auro, M., Bauch, D., Dehairs, F., Lam, P., Li, J., Maldonado, M., Mears, C., Newton, R., Pasqualini, A., Planquette, H., Rember, R., & Thomas, H. Strong margin influence on the Arctic Ocean Barium Cycle revealed by pan‐Arctic synthesis. Journal of Geophysical Research: Oceans, 127(4), (2022): e2021JC017417, https://doi.org/10.1029/2021jc017417.
    Description: Early studies revealed relationships between barium (Ba), particulate organic carbon and silicate, suggesting applications for Ba as a paleoproductivity tracer and as a tracer of modern ocean circulation. But, what controls the distribution of barium (Ba) in the oceans? Here, we investigated the Arctic Ocean Ba cycle through a one-of-a-kind data set containing dissolved (dBa), particulate (pBa), and stable isotope Ba ratio (δ138Ba) data from four Arctic GEOTRACES expeditions conducted in 2015. We hypothesized that margins would be a substantial source of Ba to the Arctic Ocean water column. The dBa, pBa, and δ138Ba distributions all suggest significant modification of inflowing Pacific seawater over the shelves, and the dBa mass balance implies that ∼50% of the dBa inventory (upper 500 m of the Arctic water column) was supplied by nonconservative inputs. Calculated areal dBa fluxes are up to 10 μmol m−2 day−1 on the margin, which is comparable to fluxes described in other regions. Applying this approach to dBa data from the 1994 Arctic Ocean Survey yields similar results. The Canadian Arctic Archipelago did not appear to have a similar margin source; rather, the dBa distribution in this section is consistent with mixing of Arctic Ocean-derived waters and Baffin Bay-derived waters. Although we lack enough information to identify the specifics of the shelf sediment Ba source, we suspect that a sedimentary remineralization and terrigenous sources (e.g., submarine groundwater discharge or fluvial particles) are contributors.
    Description: This research was supported by the National Science Foundation [OCE-1434312 (AMS), OCE-1436666 (RN), OCE-1535854 (PL), OCE-1736949, OCE-2023456 (TJH), and OCE-1829563 (R. Anderson for open access support)], Natural Sciences and Engineering Research Council of Canada (NSERC)-Climate Change and Atmospheric Research (CCAR) Program (MTM), and LEFE-CYBER EXPATE (HP). HT acknowledges support by the Canadian GEOTRACES via NSERC-CCAR and the German Academic Exchange Service (DAAD): MOPGA-GRI (Make Our Planet Great Again—Research Initiative) sponsored by BMBF (Federal German Ministry of Education and Research; Grant No. 57429828).
    Keywords: GEOTRACES ; Barium isotopes ; Geochemical cycles ; Climate ; Continental shelves
    Repository Name: Woods Hole Open Access Server
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  • 20
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    Biogeochemical iron budgets of the Southern Ocean south of Australia : decoupling of iron and nutrient cycles in the subantarctic zone by the summertime supply (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2009. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 23 (2009): GB4034, doi:10.1029/2009GB003500.
    Description: Climate change is projected to significantly alter the delivery (stratification, boundary currents, aridification of landmasses, glacial melt) of iron to the Southern Ocean. We report the most comprehensive suite of biogeochemical iron budgets to date for three contrasting sites in subantarctic and polar frontal waters south of Australia. Distinct regional environments were responsible for differences in the mode and strength of iron supply mechanisms, with higher iron stocks and fluxes observed in surface northern subantarctic waters, where atmospheric iron fluxes were greater. Subsurface waters southeast of Tasmania were also enriched with particulate iron, manganese and aluminum, indicative of a strong advective source from shelf sediments. Subantarctic phytoplankton blooms are thus driven by both seasonal iron supply from southward advection of subtropical waters and by wind-blown dust deposition, resulting in a strong decoupling of iron and nutrient cycles. We discuss the broader global significance our iron budgets for other ocean regions sensitive to climate-driven changes in iron supply.
    Description: T.W. was supported by a BDI grant from CNRS and Région PACA, by CNRS PICS project 3604, and by the “Soutien à la mer” CSOA CNRS-INSU. P.W.B. was supported by the New Zealand FRST Coasts and Oceans OBI. This research was supported by the Australian Government Cooperative Research Centres Programme through the Antarctic Climate and Ecosystems CRC (ACE CRC) and Australian Antarctic Science project 2720.
    Keywords: Iron ; Southern Ocean ; Biogeochemical budget ; Subantarctic ; Polar ; Australian sector
    Repository Name: Woods Hole Open Access Server
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