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  • 1
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    Carbon 13 in Pacific Deep and Intermediate Waters, 0-370 ka: Implications for Ocean Circulation and Pleistocene CO2 (1991)
    AGU (American Geophysical Union)
    In:  Paleoceanography, 6 (2). pp. 205-226.
    Details
    Publication Date: 2018-03-02
    Description: Stable isotopes in benthic foraminifera from Pacific sediments are used to assess hypotheses of systematic shifts in the depth distribution of oceanic nutrients and carbon during the ice ages. The carbon isotope differences between ∼1400 and ∼3200 m depth in the eastern Pacific are consistently greater in glacial than interglacial maxima over the last ∼370 kyr. This phenomenon of “bottom heavy” glacial nutrient distributions, which Boyle proposed as a cause of Pleistocene CO2 change, occurs primarily in the 1/100 and 1/41 kyr−1 “Milankovitch” orbital frequency bands but appears to lack a coherent 1/23 kyr−1 band related to orbital precession. Averaged over oxygen-isotope stages, glacial δ13C gradients from ∼1400 to ∼3200 m depth are 0.1‰ greater than interglacial gradients. The range of extreme shifts is somewhat larger, 0.2 to 0.5‰. In both cases, these changes in Pacific δ13C distributions are much smaller than observed in shorter records from the North Atlantic. This may be too small to be a dominant cause of atmospheric pCO2 change, unless current models underestimate the sensitivity of pCO2 to nutrient redistributions. This dampening of Pacific relative to Atlantic δ13C depth gradient favors a North Atlantic origin of the phenomenon, although local variations of Pacific intermediate water masses can not be excluded at present.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/90PA02303
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Atmospheric carbon dioxide, orbital forcing, and climate (1985)
    AGU (American Geophysical Union)
    In:  In: The carbon cycle and atmospheric CO2: Natural variations archean to present; Proceedings of the Chapman Conference on Natural Variations in Carbon Dioxide and the Carbon Cycle, Tarpon Springs, FL, January 9-13, 1984. AGU (American Geophysical Union), Washington, DC, pp. 303-317.
    Details
    Publication Date: 2015-08-03
    Description: A 340,000-year record of benthic and planktonic oxygen and carbon isotope measurements from an equatorial Pacific deep-sea core are analyzed. The data provide estimates of both global ice volume and atmospheric carbon dioxide concentration over this period. The frequencies characteristic of changes in the earth-sun orbital geometry dominate all the records. Examination of phase relationships shows that atmospheric carbon dioxide concentration leads ice volume over the orbital bandwidth, and is forced by orbital changes through a mechanism, at present not fully understood, with a short response time. Changes in atmospheric CO2 are not primarily caused by glacial-interglacial sea level changes, which had been hypothesized to affect atmospheric CO2 through the effect on ocean chemistry of changing sedimentation on the continental shelves. Instead, variations in atmospheric CO2 should be regarded as part of the forcing of ice volume changes.
    Type: Book chapter , NonPeerReviewed
    Format: text
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    OceanRep: Book chapter
  • 3
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    Constraints on the magnitude and patterns of ocean cooling at the Last Glacial Maximum (2009)
    In:  EPIC3Nature Geoscience, 2, pp. 127-132
    Details
    Publication Date: 2016-03-15
    Description: Observation-based reconstructions of sea surface temperature from relatively stable periods in the past, such as the Last Glacial Maximum, represent an important means of constraining climate sensitivity and evaluating model simulations1. The first quantitative global reconstruction of sea surface temperatures during the Last Glacial Maximum was developed by the Climate Long-Range Investigation, Mapping and Prediction (CLIMAP) project in the 1970s and 1980s (refs 2, 3). Since that time, several shortcomings of that earlier effort have become apparent4. Here we present an updated synthesis of sea surface temperatures during the Last Glacial Maximum, rigorously defined as the period between 23 and 19 thousand years before present, from the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) project5. We integrate microfossil and geochemical reconstructions of surface temperatures and include assessments of the reliability of individual records. Our reconstruction reveals the presence of large longitudinal gradients in sea surface temperature in all of the ocean basins, in contrast to the simulations of the Last Glacial Maximum climate available at present
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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