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  • 1
    Publication Date: 2022-01-31
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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  • 2
    Publication Date: 2021-03-16
    Description: 231Pa, 230Th and 232Th were analyzed in filtered seawater (n=70) and suspended particles (n=39) collected along a shelf-basin transect from the Barents shelf to the Makarov Basin in the Arctic Ocean during GEOTRACES section GN04 in 2015. The distribution of dissolved 231Pa and 230Th in the Arctic Ocean deviates from the linear increase expected from reversible scavenging. Higher 232Th concentrations were observed at the shelf, slope and in surface waters in the deep basin, pointing at lithogenic sources. Fractionation factors (FTh/Pa) observed at the Nansen margin were higher compared to FTh/Pa in the central Nansen Basin, possibly due to the residual occurrence of hydrothermal particles in the deep central Nansen Basin. Application of a boundary scavenging model quantitatively accounts for the dissolved and particulate 230Th distributions in the Nansen Basin. Modelled dissolved 231Pa distributions were largely overestimated, which was attributed to the absence of incorporation of water exchange with the Atlantic Ocean in the model. 231Pa/230Th ratios of the suspended particles of the Nansen Basin were below the 231Pa/230Th production ratio, but top-core sediments of the Nansen margin and slope have high 231Pa/230Th-ratios, suggesting that scavenging along the Nansen margin partly acts as a sink for the missing Arctic 231Pa.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 3
    Publication Date: 2020-02-26
    Description: 230Th‐normalization is a valuable paleoceanographic tool for reconstructing high‐resolution sediment fluxes during the late Pleistocene (last ~500,000 years). As its application has expanded to ever more diverse marine environments, the nuances of 230Th systematics, with regards to particle type, particle size, lateral advective/diffusive redistribution, and other processes, have emerged. We synthesized over 1000 sedimentary records of 230Th from across the global ocean at two time slices, the Late Holocene (0‐5000 years ago, or 0‐5 ka) and the Last Glacial Maximum (18.5‐23.5 ka), and investigated the spatial structure of 230Th‐normalized mass fluxes. On a global scale, sedimentary mass fluxes were significantly higher during the Last Glacial Maximum (1.79‐2.17 g/cm2kyr, 95% confidence) relative to the Holocene (1.48‐1.68 g/cm2kyr, 95% confidence). We then examined the potential confounding influences of boundary scavenging, nepheloid layers, hydrothermal scavenging, size dependent sediment fractionation, and carbonate dissolution on the efficacy of 230Th as a constant flux proxy. Anomalous 230Th behavior is sometimes observed proximal to hydrothermal ridges and in continental margins where high particle fluxes and steep continental slopes can lead to the combined effects of boundary scavenging and nepheloid interference. Notwithstanding these limitations, we found that 230Th‐normalization is a robust tool for determining sediment mass accumulation rates in the majority of pelagic marine settings (〉 1000 m water depth).
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 4
    Publication Date: 2018-08-08
    Description: In seawater, particle reactive 231Pa and 230Th are uniformly produced by decay of soluble 235U and 234U. Due to differences in particle reactivity, 230Th tends to be removed to the sediment close to its production site, while 231Pa is more prone to lateral transport and is removed to the sediments in areas of high particle flux (i.e. boundary scavenging). Due to a combination of perennial ice cover, large shelf areas and river runoff, boundary scavenging in the Arctic Ocean strongly impacts the distribution of 231Pa and 230Th in the water column. Here, 231Pa and 230Th were analyzed in seawater and particles from the Arctic GEOTRACES section GN04 along the Barents shelf and in the Nansen basin. Key observations include lower concentrations of dissolved 231Pa and 230Th on the Barents shelf compared to the Nansen basin, indicating enhanced removal of 231Pa and 230Th near the margin. The particulate nuclide/total nuclide ratio increases from the surface (0.2% for 231Paxs and 0.7% for 230Thxs) to the seafloor (11% for 231Paxs and 71% for 230Thxs), highlighting the role of deep scavenging. The fractionation factor between 231Pa and 230Th (FTh/Pa) ranges from ~3 to 25 and generally increases with depth. Comparison between suspended particles and sediments will be provided. Further, dissolved 231Paxs and 230Thxs concentrations in the Nansen basin are lower compared to concentrations measured 20 years ago1 . This might reflect changes in particle flux and/or changes in circulation patterns. 1 Scholten, J., Rutgers van der Loeff, M., 1995. Distribution of 230Th and 231Pa in the water column in relation to the ventilation of the deep Arctic basins. Deep. Res. Part II 42, 1519–1531.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 5
    Publication Date: 2020-02-13
    Description: Rapid changes in ocean circulation and climate have been observed in marine-sediment and ice cores over the last glacial period and deglaciation, highlighting the non-linear character of the climate system and underlining the possibility of rapid climate shifts in response to anthropogenic greenhouse gas forcing. To date, these rapid changes in climate and ocean circulation are still not fully explained. One obstacle hindering progress in our understanding of the interactions between past ocean circulation and climate changes is the difficulty of accurately dating marine cores. Here, we present a set of 92 marine sediment cores from the Atlantic Ocean for which we have established age-depth models that are consistent with the Greenland GICC05 ice core chronology, and computed the associated dating uncertainties, using a new deposition modeling technique. This is the first set of consistently dated marine sediment cores enabling paleoclimate scientists to evaluate leads/lags between circulation and climate changes over vast regions of the Atlantic Ocean. Moreover, this data set is of direct use in paleoclimate modeling studies.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 6
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Waelbroeck, C., Lougheed, B. C., Riveiros, N. V., Missiaen, L., Pedro, J., Dokken, T., Hajdas, I., Wacker, L., Abbott, P., Dumoulin, J., Thil, F., Eynaud, F., Rossignol, L., Fersi, W., Albuquerque, A. L., Arz, H., Austin, W. E. N., Came, R., Carlson, A. E., Collins, J. A., Dennielou, B., Desprat, S., Dickson, A., Elliot, M., Farmer, C., Giraudeau, J., Gottschalk, J., Henderiks, J., Hughen, K., Jung, S., Knutz, P., Lebreiro, S., Lund, D. C., Lynch-Stieglitz, J., Malaize, B., Marchitto, T., Martinez-Mendez, G., Mollenhauer, G., Naughton, F., Nave, S., Nuernberg, D., Oppo, D., Peck, V., Peeters, F. J. C., Penaud, A., Portilho-Ramos, R. d. C., Repschlaeger, J., Roberts, J., Ruehlemann, C., Salgueiro, E., Goni, M. F. S., Schonfeld, J., Scussolini, P., Skinner, L. C., Skonieczny, C., Thornalley, D., Toucanne, S., Van Rooij, D., Vidal, L., Voelker, A. H. L., Wary, M., Weldeab, S., & Ziegler, M. Consistently dated Atlantic sediment cores over the last 40 thousand years. Scientific Data, 6, (2019): 165, doi:10.1038/s41597-019-0173-8.
    Description: Rapid changes in ocean circulation and climate have been observed in marine-sediment and ice cores over the last glacial period and deglaciation, highlighting the non-linear character of the climate system and underlining the possibility of rapid climate shifts in response to anthropogenic greenhouse gas forcing. To date, these rapid changes in climate and ocean circulation are still not fully explained. One obstacle hindering progress in our understanding of the interactions between past ocean circulation and climate changes is the difficulty of accurately dating marine cores. Here, we present a set of 92 marine sediment cores from the Atlantic Ocean for which we have established age-depth models that are consistent with the Greenland GICC05 ice core chronology, and computed the associated dating uncertainties, using a new deposition modeling technique. This is the first set of consistently dated marine sediment cores enabling paleoclimate scientists to evaluate leads/lags between circulation and climate changes over vast regions of the Atlantic Ocean. Moreover, this data set is of direct use in paleoclimate modeling studies.
    Description: The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Program (FP7/2007-2013 Grant agreement n° 339108). New 14C dates for cores EW9209-1JPC and V29-202 were funded by NSF OCE grants to DWO. FN, ES and AV acknowledge FCT funding support through project UID/Multi/04326/2019. We thank T. Garlan and P. Guyomard for having given us access to cores from the Service Hydrographique et Océanographique de la Marine. We acknowledge N. Smialkowski for help with formatting the data into text files, and L. Mauclair, L. Leroy and G. Isguder for the picking of numerous foraminifer samples for radiocarbon dating. We are grateful to S. Obrochta, E. Cortijo, E. Michel, F. Bassinot, J.C. Duplessy, and L. Labeyrie for advice and fruitful discussions. This paper is LSCE contribution 6572.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 7
    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Hayes, C. T., Costa, K. M., Anderson, R. F., Calvo, E., Chase, Z., Demina, L. L., Dutay, J., German, C. R., Heimburger-Boavida, L., Jaccard, S. L., Jacobel, A., Kohfeld, K. E., Kravchishina, M. D., Lippold, J., Mekik, F., Missiaen, L., Pavia, F. J., Paytan, A., Pedrosa-Pamies, R., Petrova, M., V., Rahman, S., Robinson, L. F., Roy-Barman, M., Sanchez-Vidal, A., Shiller, A., Tagliabue, A., Tessin, A. C., van Hulten, M., & Zhang, J. Global ocean sediment composition and burial flux in the deep sea. Global Biogeochemical Cycles, 35(4), (2021): e2020GB006769, https://doi.org/10.1029/2020GB006769.
    Description: Quantitative knowledge about the burial of sedimentary components at the seafloor has wide-ranging implications in ocean science, from global climate to continental weathering. The use of 230Th-normalized fluxes reduces uncertainties that many prior studies faced by accounting for the effects of sediment redistribution by bottom currents and minimizing the impact of age model uncertainty. Here we employ a recently compiled global data set of 230Th-normalized fluxes with an updated database of seafloor surface sediment composition to derive atlases of the deep-sea burial flux of calcium carbonate, biogenic opal, total organic carbon (TOC), nonbiogenic material, iron, mercury, and excess barium (Baxs). The spatial patterns of major component burial are mainly consistent with prior work, but the new quantitative estimates allow evaluations of deep-sea budgets. Our integrated deep-sea burial fluxes are 136 Tg C/yr CaCO3, 153 Tg Si/yr opal, 20Tg C/yr TOC, 220 Mg Hg/yr, and 2.6 Tg Baxs/yr. This opal flux is roughly a factor of 2 increase over previous estimates, with important implications for the global Si cycle. Sedimentary Fe fluxes reflect a mixture of sources including lithogenic material, hydrothermal inputs and authigenic phases. The fluxes of some commonly used paleo-productivity proxies (TOC, biogenic opal, and Baxs) are not well-correlated geographically with satellite-based productivity estimates. Our new compilation of sedimentary fluxes provides detailed regional and global information, which will help refine the understanding of sediment preservation.
    Description: This study was supported by the Past Global Changes (PAGES) project, which in turn received support from the Swiss Academy of Sciences and the US-NSF. The work grew out of a 2018 workshop in Aix-Marseille, France, funded by PAGES, GEOTRACES, SCOR, US-NSF, Aix Marseille Université, and John Cantle Scientific, and the authors would like to acknowledge all attendees of this meeting. The authors acknowledge the participants of the 68th cruise of RV Akademik Mstislav Keldysh for helping acquire samples. Christopher T. Hayes acknowledges support from US-NSF awards 1658445 and 1737023. Some data compilation on Arctic shelf seas was supported by the Russian Science Foundation, grant number 20-17-00157. This work was also supported through project CRESCENDO (grant no. 641816, European Commission). Zanna Chase acknowledges support from the Australian Research Council’s Discovery Projects funding scheme (project DP180102357). Christopher R. German acknowledges US-NSF awards 1235248 and 1234827. Some colorbars used in the figures were designed by Kristen Thyng et al. (2016) and Patrick Rafter.
    Keywords: Barium ; Carbon cycle ; Marine atlas ; Mercury ; Opal ; Sediment burial
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 8
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Costa, K. M., Hayes, C. T., Anderson, R. F., Pavia, F. J., Bausch, A., Deng, F., Dutay, J., Geibert, W., Heinze, C., Henderson, G., Hillaire-Marcel, C., Hoffmann, S., Jaccard, S. L., Jacobel, A. W., Kienast, S. S., Kipp, L., Lerner, P., Lippold, J., Lund, D., Marcantonio, F., McGee, D., McManus, J. F., Mekik, F., Middleton, J. L., Missiaen, L., Not, C., Pichat, S., Robinson, L. F., Rowland, G. H., Roy-Barman, M., Alessandro, Torfstein, A., Winckler, G., & Zhou, Y. 230 Th normalization: new insights on an essential tool for quantifying sedimentary fluxes in the modern and quaternary ocean. Paleoceanography and Paleoclimatology, 35(2), (2020): e2019PA003820, doi:10.1029/2019PA003820.
    Description: 230Th normalization is a valuable paleoceanographic tool for reconstructing high‐resolution sediment fluxes during the late Pleistocene (last ~500,000 years). As its application has expanded to ever more diverse marine environments, the nuances of 230Th systematics, with regard to particle type, particle size, lateral advective/diffusive redistribution, and other processes, have emerged. We synthesized over 1000 sedimentary records of 230Th from across the global ocean at two time slices, the late Holocene (0–5,000 years ago, or 0–5 ka) and the Last Glacial Maximum (18.5–23.5 ka), and investigated the spatial structure of 230Th‐normalized mass fluxes. On a global scale, sedimentary mass fluxes were significantly higher during the Last Glacial Maximum (1.79–2.17 g/cm2kyr, 95% confidence) relative to the Holocene (1.48–1.68 g/cm2kyr, 95% confidence). We then examined the potential confounding influences of boundary scavenging, nepheloid layers, hydrothermal scavenging, size‐dependent sediment fractionation, and carbonate dissolution on the efficacy of 230Th as a constant flux proxy. Anomalous 230Th behavior is sometimes observed proximal to hydrothermal ridges and in continental margins where high particle fluxes and steep continental slopes can lead to the combined effects of boundary scavenging and nepheloid interference. Notwithstanding these limitations, we found that 230Th normalization is a robust tool for determining sediment mass accumulation rates in the majority of pelagic marine settings (〉1,000 m water depth).
    Description: We thank Zanna Chase and one anonymous reviewer for valuable feedback. K. M. C. was supported by a Postdoctoral Scholarship at WHOI. L. M. acknowledges funding from the Australian Research Council grant DP180100048. The contribution of C. T. H., J. F. M., and R. F. A. were supported in part by the U.S. National Science Foundation (US‐NSF). G. H. R. was supported by the Natural Environment Research Council (grant NE/L002434/1). S. L. J. acknowledges support from the Swiss National Science Foundation (grants PP002P2_144811 and PP00P2_172915). This study was supported by the Past Global Changes (PAGES) project, which in turn received support from the Swiss Academy of Sciences and the US‐NSF. This work grew out of a 2018 workshop in Aix‐Marseille, France, funded by PAGES, GEOTRACES, SCOR, US‐NSF, Aix‐Marseille Université, and John Cantle Scientific. All data are publicly available as supporting information to this document and on the National Center for Environmental Information (NCEI) at https://www.ncdc.noaa.gov/paleo/study/28791.
    Keywords: Thorium ; Sediment flux ; Holocene ; LGM ; GEOTRACES
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 9
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    In:  Supplement to: Missiaen, Lise; Waelbroeck, Claire; Pichat, Sylvain; Jaccard, Samuel L; Eynaud, Frédérique; Greenop, Rosanna; Burke, Andrea (2019): Improving North Atlantic marine core chronologies using 230Th‐normalization. Paleoceanography and Paleoclimatology, https://doi.org/10.1029/2018PA003444
    Publication Date: 2023-01-13
    Description: Tables S01 to S12 and marine sediment core SU90-08 Sea Surface Temperature reconstruction over the last 40 ka. Table S01: 238U, 232Th, 230Th activities measured in SU90-03 bulk samples Table S02: 14C ages used in this study for core SU81-18 Table S03: 14C ages used in this study for core SU90-03 Table S04: 14C ages used in this study for core MD03-2705 Table S05: 14C ages used in this study for core SU90-08 Table S06: Alignment tie-points for SU90-08 Table S07: Alignment tie-points for SU90-03 Table S08: Alignment tie-points for SU81-18 Table S09: SU90-08 230Th-normalized age model Table S10: SU90-03 Th-normalized age model Table S11: SU81-18 230Th-normalized age model Table S12: Impact of temporal variations of (U/Th)det on Th-normalization based chronologies for the studied cores
    Type: Dataset
    Format: application/zip, 13 datasets
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  • 10
    Publication Date: 2023-01-13
    Type: Dataset
    Format: application/zip, 408 Bytes
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