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  • 2015-2019  (12)
  • 2016  (4)
  • 2015  (8)
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  • 2015-2019  (12)
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  • 1
    Publication Date: 2019-02-25
    Description: Fossils of marine microorganisms such as planktic foraminifera are among the cornerstones of palaeoclimatological studies. It is often assumed that the proxies derived from their shells represent ocean conditions above the location where they were deposited. Planktic foraminifera, however, are carried by ocean currents and, depending on the life traits of the species, potentially incorporate distant ocean conditions. Here we use high-resolution ocean models to assess the footprint of planktic foraminifera and validate our method with proxy analyses from two locations. Results show that foraminifera, and thus recorded palaeoclimatic conditions, may originate from areas up to several thousands of kilometres away, reflecting an ocean state significantly different from the core site. In the eastern equatorial regions and the western boundary current extensions, the offset may reach 1.5 °C for species living for a month and 3.0 °C for longer-living species. Oceanic transport hence appears to be a crucial aspect in the interpretation of proxy signals.
    Type: Article , PeerReviewed
    Format: text
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  • 2
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    PANGAEA
    In:  Supplement to: Jonkers, Lukas; Zahn, Rainer; Thomas, Alexander; Henderson, Gideon M; Abouchami, Wafa; Francois, Roger; Masqué, Pere; Hall, Ian R; Bickert, Torsten (2015): Deep circulation changes in the central South Atlantic during the past 145 kyrs reflected in a combined 231Pa/230Th, Neodymium isotope and benthic d13C record. Earth and Planetary Science Letters, 419, 14-21, https://doi.org/10.1016/j.epsl.2015.03.004
    Publication Date: 2023-07-05
    Description: Previous work showed that South Atlantic sediments have lower glacial than Holocene 231Pa/230Th, which was attributed to a switch in the flow direction of Atlantic deep-water. Debate exists, however as to the degree to which two processes - circulation and scavenging - determine sedimentary 231Pa/230Th, making this interpretation contentious. Here we address this issue using 145-kyr records of paleocirculation proxies. Benthic foraminiferal d13C, neodymium isotopes (ENd) and sedimentary 231Pa/230Th were all measured in a single sediment core from the South Atlantic subtropical gyre. This site largely excludes the influence of local productivity changes on 231Pa/230Th records. Measured 231Pa/230Th ranges between ~0.041 during glacials to ~0.055 during interglacial periods and are consistently lower than the production ratio, indicating export of 231Pa from the central South Atlantic for the entire duration of the record. The lower glacial 231Pa/230Th is regionally consistent, suggesting that basin-scale oceanographic processes cause the decrease. In turn, less radiogenic ENd and lower benthic d13C confirm the classical picture of an increase in Southern Component Water (SCW) influence in the Atlantic during glacial periods and point to a circulation control on the observed 231Pa/230Th decrease rather than a local productivity change. We suggest that associated with this change in water mass distribution the dominant sink for 231Pa shifted from the margins of the South Atlantic and/or the Southern Ocean during interglacials, to the North Atlantic during glacial periods. Indeed, elevated 231Pa/230Th in the deep North Atlantic during glacials supports this mechanism of northward transport of 231Pa by SCW.
    Keywords: Center for Marine Environmental Sciences; GeoB; Geosciences, University of Bremen; MARUM
    Type: Dataset
    Format: application/zip, 3 datasets
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  • 3
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    PANGAEA
    In:  Supplement to: Wei, Ran; Abouchami, Wafa; Zahn, Rainer; Masqué, Pere (2016): Deep circulation changes in the South Atlantic since the Last Glacial Maximum from Nd isotope and multi-proxy records. Earth and Planetary Science Letters, 434, 18-29, https://doi.org/10.1016/j.epsl.2015.11.001
    Publication Date: 2023-07-05
    Description: We report down-core sedimentary Nd isotope (epsilon Nd) records from two South Atlantic sediment cores, MD02-2594 and GeoB3603-2, located on the western South African continental margin. The core sites are positioned downstream of the present-day flow path of North Atlantic Deep Water (NADW) and close to the Southern Ocean, which makes them suitable for reconstructing past variability in NADW circulation over the last glacial cycle. The Fe-Mn leachates epsilon Nd records show a coherent decreasing trend from glacial radiogenic values towards less radiogenic values during the Holocene. This trend is confirmed by epsilon Nd in fish debris and mixed planktonic foraminifera, albeit with an offset during the Holocene to lower values relative to the leachates, matching the present-day composition of NADW in the Cape Basin. We interpret the epsilon Nd changes as reflecting the glacial shoaling of Southern Ocean waters to shallower depths combined with the admixing of southward flowing Northern Component Water (NCW). A compilation of Atlantic epsilon Nd records reveals increasing radiogenic isotope signatures towards the south and with increasing depth. This signal is most prominent during the Last Glacial Maximum (LGM) and of similar amplitude across the Atlantic basin, suggesting continuous deep water production in the North Atlantic and export to the South Atlantic and the Southern Ocean. The amplitude of the epsilon Nd change from the LGM to Holocene is largest in the southernmost cores, implying a greater sensitivity to the deglacial strengthening of NADW at these sites. This signal impacted most prominently the South Atlantic deep and bottom water layers that were particularly deprived of NCW during the LGM. The epsilon Nd variations correlate with changes in 231Pa/230Th ratios and benthic d13C across the deglacial transition. Together with the contrasting 231Pa/230Th: epsilon Nd pattern of the North and South Atlantic, this indicates a progressive reorganization of the AMOC to full strength during the Holocene.
    Type: Dataset
    Format: application/zip, 3 datasets
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  • 4
    Publication Date: 2023-07-05
    Keywords: AGE; CALYPSO; Calypso Corer; Depth, bottom/max; DEPTH, sediment/rock; Depth, top/min; Marion Dufresne (1995); MD02-2594; MD128; Method comment; Neodymium-143/Neodymium-144 ratio; Neodymium-143/Neodymium-144 ratio, error; Sample type; Southern Ocean; Strontium-87/Strontium-86 ratio; Strontium-87/Strontium-86 ratio, error; SWAF; ε-Neodymium; ε-Neodymium, error
    Type: Dataset
    Format: text/tab-separated-values, 494 data points
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  • 5
    Publication Date: 2023-07-05
    Keywords: AGE; CALYPSO; Calypso Corer; Depth, bottom/max; DEPTH, sediment/rock; Depth, top/min; Marion Dufresne (1995); MD02-2594; MD128; Neodymium-143/Neodymium-144 ratio; Neodymium-143/Neodymium-144 ratio, error; Sample type; Southern Ocean; Strontium-87/Strontium-86 ratio; Strontium-87/Strontium-86 ratio, error; SWAF; ε-Neodymium; ε-Neodymium, error
    Type: Dataset
    Format: text/tab-separated-values, 134 data points
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  • 6
    Publication Date: 2024-01-09
    Keywords: 161-976; AGE; Alboran Sea; COMPCORE; Composite Core; DEPTH, sediment/rock; DSDP/ODP/IODP sample designation; Globigerina bulloides, Magnesium/Calcium ratio; Globigerina bulloides, δ18O; Joides Resolution; Leg161; Ocean Drilling Program; ODP; Sample code/label; Sea surface temperature, annual mean; SST from Mg/Ca ratios
    Type: Dataset
    Format: text/tab-separated-values, 1232 data points
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  • 7
    Publication Date: 2024-01-09
    Keywords: 161-976; AGE; Alboran Sea; COMPCORE; Composite Core; DEPTH, sediment/rock; DSDP/ODP/IODP sample designation; Globigerina bulloides, Magnesium/Calcium ratio; Globigerina bulloides, δ18O; Joides Resolution; Leg161; Ocean Drilling Program; ODP; Sample code/label; Sea surface temperature, annual mean; SST from Mg/Ca ratios
    Type: Dataset
    Format: text/tab-separated-values, 1071 data points
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  • 8
    Publication Date: 2024-02-02
    Keywords: AGE; Calcium/Iron ratio; Center for Marine Environmental Sciences; DEPTH, sediment/rock; Foraminifera, benthic δ13C; Foraminifera, benthic δ18O; GeoB; GeoB3808-6; Geosciences, University of Bremen; Gravity corer (Kiel type); M34/3; MARUM; Meteor (1986); Mid Atlantic Ridge; SL
    Type: Dataset
    Format: text/tab-separated-values, 254 data points
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  • 9
    Publication Date: 2024-02-02
    Keywords: Center for Marine Environmental Sciences; DEPTH, sediment/rock; GeoB; GeoB3808-6; Geosciences, University of Bremen; Gravity corer (Kiel type); M34/3; MARUM; Meteor (1986); Mid Atlantic Ridge; Neodymium-143/Neodymium-144 ratio; Neodymium-143/Neodymium-144 ratio, error; SL; Strontium-87/Strontium-86 ratio; Strontium-87/Strontium-86 ratio, error; ε-Neodymium; ε-Neodymium, standard deviation
    Type: Dataset
    Format: text/tab-separated-values, 202 data points
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  • 10
    Publication Date: 2024-02-02
    Keywords: Center for Marine Environmental Sciences; DEPTH, sediment/rock; GeoB; GeoB3808-6; Geosciences, University of Bremen; Gravity corer (Kiel type); M34/3; MARUM; Meteor (1986); Mid Atlantic Ridge; Protactinium-231; Protactinium-231, standard deviation; Protactinium-231/Thorium-230 excess, decay-corrected; Protactinium-231/Thorium-230 excess, decay-corrected, standard deviation; SL; Thorium-230; Thorium-230, standard deviation; Thorium-232; Thorium-232, standard deviation; Uranium-238; Uranium-238, standard deviation
    Type: Dataset
    Format: text/tab-separated-values, 480 data points
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