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  • 1
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    PANGAEA
    In:  Supplement to: Broecker, Wallace S; Clark, Elizabeth; Barker, Stephen; Hajdas, Irena; Bonani, Georges; Moreno, Eva (2007): Radiocarbon age of late glacial deep water from the equatorial Pacific. Paleoceanography, 22(2), PA2206, https://doi.org/10.1029/2006PA001359
    Publication Date: 2023-05-12
    Description: Radiocarbon age differences for pairs of coexisting late glacial age benthic and planktic foraminifera shells handpicked from 10 sediment samples from a core from a depth of 2.8 km in the western equatorial Pacific are not significantly different from that of 1600 years calculated from measurements on prenuclear seawater. This places a lower limit on the depth of the interface for the hypothetical radiocarbon-depleted glacial age seawater reservoir required to explain the 190 per mil drop in the 14C/C for atmospheric CO2, which occurred during the mystery interval (17.5 to 14.5 calendar years ago). These measurements restrict the volume of this reservoir to be no more than 35% that of the ocean. Further, 14C measurements on a single Last Glacial Maximum age sample from a central equatorial Pacific core from a depth of 4.4 km water fail to reveal evidence for the required 5- to 7-kyr age difference between benthic and planktic foraminifera shells if the isolated reservoir occupied only one third of the ocean. Nor does the 13C record for benthic forams from this abyssal core yield any evidence for the excess respiration CO2 expected to be produced during thousands of years of isolation. Nor, as indicated by the presence of benthic foraminifera, was the dissolved oxygen used up in this abyssal water.
    Type: Dataset
    Format: application/zip, 2 datasets
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  • 2
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    PANGAEA
    In:  Supplement to: Broecker, Wallace S; Barker, Stephen; Clark, Elizabeth; Hajdas, Irka; Bonani, Georges (2006): Anomalous radiocarbon ages for foraminifera shells. Paleoceanography, 21(2), PA2008, https://doi.org/10.1029/2005PA001212
    Publication Date: 2023-05-12
    Description: The causes for discordant radiocarbon results on multiple species of planktonic foraminifera from high-sedimentation-rate marine sediments are investigated. We have documented two causes for these anomalous results. One is the addition of secondary radiocarbon for which we have, to date, only one firm example. It involves an opal-rich sediment. The other is the incorporation of reworked material. Again, we have, to date, only one firm example. It involves a rapidly deposited ocean margin sediment. However, we have three other examples where reworking is the most likely explanation. On the basis of this study it is our conclusion that, where precise radiocarbon dating of high-deposition-rate marine sediment is required, a prerequisite is to demonstrate that concordant ages can be obtained on pairs of fragile and robust planktic shells. For sediment rich in opal, it is advisable to check for secondary calcite by comparing ages obtained on acid-leached samples with those on unleached samples.
    Type: Dataset
    Format: application/zip, 4 datasets
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  • 3
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    PANGAEA
    In:  Supplement to: Barker, Stephen; Kiefer, Thorsten; Elderfield, Henry (2004): Temporal changes in North Atlantic circulation constrained by planktonic foraminiferal shell weights. Paleoceanography, 19(3), PA3008, https://doi.org/10.1029/2004PA001004
    Publication Date: 2023-05-12
    Description: Records of planktonic foraminiferal shell weights for Globigerina bulloides, covering Termination I from four proximal sites at waters depths from 1150 to 4045 m in the northeast Atlantic, demonstrate the influence of dissolution superimposed upon initial shell weight variability. Records of shell weight, unaffected by dissolution, may be used as a reference for interpreting deeper records in terms of preservation history. Combining records of planktonic shell weight (and benthic d13C) from shallow and deep sites suggests that maximum oceanic stratification and incursion of southern sourced deep waters in the North Atlantic occurred at about 18-20 ka, defining the glacial mode of Atlantic circulation. Reduced stratification and enhanced preservation in deeper waters reflect conditions during Heinrich event 1. A state similar to the modern mode of Atlantic circulation was attained by about 10 ka.
    Type: Dataset
    Format: application/zip, 2 datasets
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  • 4
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    PANGAEA
    In:  Supplement to: Hasenclever, Jörg; Knorr, Gregor; Rüpke, Lars H; Köhler, Peter; Morgan, Jason Phipps; Garofalo, Kristin; Barker, Stephen; Lohmann, Gerrit; Hall, Ian R (2017): Sea level fall during glaciation stabilized atmospheric CO2 by enhanced volcanic degassing. Nature Communications, 8, 15867, https://doi.org/10.1038/ncomms15867
    Publication Date: 2023-01-13
    Description: Paleo-climate records and geodynamic modelling indicate the existence of complex interactions between glacial sea level changes, volcanic degassing, and atmospheric CO2, which may have modulated the climate system's descent into the last ice age. Between ~85-70 ka, during an interval of decreasing axial tilt, the orbital component in global temperature records gradually declined, while atmospheric CO2, instead of continuing is long-term correlation with Antarctic temperature, remained relatively stable. Based on novel global geodynamic models and the joint interpretation of paleo-proxy data as well as biogeochemical simulations, we show that a sea level fall in this interval caused enhanced pressure-release melting in the uppermost mantle, which may have induced a surge in magma and CO2 fluxes from mid-ocean ridges and oceanic hotspot volcanoes. Our results reveal a hitherto unrecognised negative feedback between glaciation and atmospheric CO2 predominantly controlled by marine volcanism on multi-millennial (suborbital) timescales of ~ 5,000-15,000 years.
    Keywords: File content; File format; File name; File size; Uniform resource locator/link to file
    Type: Dataset
    Format: text/tab-separated-values, 10 data points
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  • 5
    Publication Date: 2023-02-21
    Keywords: LIT; Literary studies; MARGO; MARGO_0000; Multiproxy Approach for the Reconstruction of the Glacial Ocean surface
    Type: Dataset
    Format: text/html, 16.4 kBytes
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  • 6
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    PANGAEA
    In:  Supplement to: Barker, Stephen; Cacho, Isabel; Benway, Heather M; Tachikawa, Kazuyo (2005): Planktonic foraminiferal Mg/Ca as a proxy for past oceanic temperatures: a methodological overview and data compilation for the Last Glacial Maximum. Quaternary Science Reviews, 24(7-9), 821-834, https://doi.org/10.1016/j.quascirev.2004.07.016
    Publication Date: 2023-02-21
    Description: As part of the Multi-proxy Approach for the Reconstruction of the Glacial Ocean (MARGO) incentive, published and unpublished temperature reconstructions for the Last Glacial Maximum (LGM) based on planktonic foraminiferal Mg/Ca ratios have been synthesised and made available in an online database. Development and applications of Mg/Ca thermometry are described in order to illustrate the current state of the method. Various attempts to calibrate foraminiferal Mg/Ca ratios with temperature, including culture, trap and core-top approaches have given very consistent results although differences in methodological techniques can produce offsets between laboratories which need to be assessed and accounted for where possible. Dissolution of foraminiferal calcite at the sea-floor generally causes a lowering of Mg/Ca ratios. This effect requires further study in order to account and potentially correct for it if dissolution has occurred. Mg/Ca thermometry has advantages over other paleotemperature proxies including its use to investigate changes in the oxygen isotopic composition of seawater and the ability to reconstruct changes in the thermal structure of the water column by use of multiple species from different depth and or seasonal habitats. Presently available data are somewhat limited to low latitudes where they give fairly consistent values for the temperature difference between Late Holocene and the LGM (2-3.5 °C). Data from higher latitudes are more sparse, and suggest there may be complicating factors when comparing between multi-proxy reconstructions.
    Keywords: LIT; Literary studies; MARGO; MARGO_0000; Multiproxy Approach for the Reconstruction of the Glacial Ocean surface
    Type: Dataset
    Format: application/zip, 2 datasets
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  • 7
    Publication Date: 2023-02-21
    Keywords: LIT; Literary studies; MARGO; MARGO_0000; Multiproxy Approach for the Reconstruction of the Glacial Ocean surface
    Type: Dataset
    Format: text/html, 16.4 kBytes
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  • 8
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    PANGAEA
    In:  Supplement to: Hall, Ian R; Boessenkool, K P; Barker, S; McCave, I Nick; Elderfield, Henry (2010): Surface and deep ocean coupling in the subpolar North Atlantic during the last 230 years. Paleoceanography, 25(2), https://doi.org/10.1029/2009PA001886
    Publication Date: 2023-02-12
    Description: The subpolar North Atlantic Ocean (SPNA) is of key importance for modulating the climate of NW Europe because of heat loss to the atmosphere from the North Atlantic Current. Although hydrographic properties of the surface SPNA vary on interannual to multidecadal timescales, hydrographic time series scarcely extend back beyond the 1950s. We present a 230 year long record of SPNA surface conditions reconstructed from a very high accumulation rate core that also registers changes in deep flow speed in the Iceland Basin. A lagged correlation is observed between the records of deep flow speed and stable oxygen isotopic composition of the surface SPNA (δ18Ow), with strongest correlation when the paleoflow speed record leads by 15–20 years. This offset may to some extent reflect size‐selective biological mixing of the sediment. Nonetheless, these records reveal a decadal‐scale coupling between surface and deep ocean variability over the past 230 years, possibly driven by the North Atlantic Oscillation, with implications for North Atlantic circulation and climate.
    Keywords: Age; AGE; BC; Box corer; CD159; Charles Darwin; DEPTH, sediment/rock; Gardar Drift; Globigerina bulloides, δ18O; RAPiD-21-12B; Sea surface temperature; Size fraction 250–315 μm; SST from Mg/Ca ratios
    Type: Dataset
    Format: text/tab-separated-values, 261 data points
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  • 9
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    PANGAEA
    In:  Supplement to: Anderson, Robert F; Barker, Stephen; Fleisher, Martin Q; Gersonde, Rainer; Goldstein, Steven L; Kuhn, Gerhard; Mortyn, P Graham; Pahnke, Katharina; Sachs, Julian P (2014): Biological response to millennial variability of dust and nutrient supply in the Subantarctic South Atlantic Ocean. Philosophical Transactions of the Royal Society A-Mathematical Physical and Engineering Sciences, 372(2019), 20130054, https://doi.org/10.1098/rsta.2013.0054
    Publication Date: 2023-03-16
    Description: Fluxes of lithogenicmaterial and fluxes of three palaeo productivity proxies (organic carbon, biogenic opal and alkenones) over the past 100,000 years were determined using the 230Th-normalization method in three sediment cores from the Subantarctic South Atlantic Ocean. Features in the lithogenic flux record of each core correspond to similar features in the record of dust deposition in the EPICA Dome C ice core. Biogenic fluxes correlate with lithogenic fluxes in each sediment core. Our preferred interpretation is that South American dust, most probably from Patagonia, constitutes a major source of lithogenic material in Subantarctic South Atlantic sediments, and that past biological productivity in this region responded to variability in the supply of dust, probably due to biologically available iron carried by the dust. Greater nutrient supply as well as greater nutrient utilization (stimulated by dust) contributed to Subantarctic productivity during cold periods, in contrast to the region south of the Antarctic Polar Front (APF), where reduced nutrient supply during cold periods was the principal factor limiting productivity. The anti-phased patterns of productivity on opposite sides of the APF point to shifts in the physical supply of nutrients and to dust as cofactors regulating productivity in the Southern Ocean.
    Keywords: AWI_Paleo; Paleoenvironmental Reconstructions from Marine Sediments @ AWI
    Type: Dataset
    Format: application/zip, 3 datasets
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  • 10
    Publication Date: 2023-05-12
    Keywords: Age, 14C AMS; Age, dated; Age, dated material; Age, dated standard deviation; Central Pacific; Depth, bottom/max; DEPTH, sediment/rock; Depth, top/min; Event label; MUC; MultiCorer; PC; Piston corer; TTN13-18; TTN13-19
    Type: Dataset
    Format: text/tab-separated-values, 60 data points
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