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Publication Detail
Atmospheric carbon dioxide through the Eocene-Oligocene climate transition
  • Publication Type:
    Journal article
  • Publication Sub Type:
    Journal Article
  • Authors:
    Pearson PN, Foster GL, Wade BS
  • Publication date:
    22/10/2009
  • Pagination:
    1110, 1113
  • Journal:
    Nature
  • Volume:
    461
  • Issue:
    7267
  • Status:
    Published
  • Print ISSN:
    0028-0836
Abstract
Geological and geochemical evidence1-3 indicates that the Antarctic ice sheet formed during the Eocene-Oligocene transition4, 33.5-34.0 million years ago. Modelling studies5,6 suggest that such ice-sheet formation might have been triggered when atmospheric carbon dioxide levels (pco2atm) fell below a critical threshold, of ∼750 p.p.m.v., but the timing and. magnitude of pco2atm relative to the evolution of the ice sheet has remained unclear. Here we use the boron isotope pH proxy7'8 on exceptionally well-preserved carbonate microfossils from a recently discovered geological section in Tanzania9'10 to estimate pco2atm before, during and after the climate transition. Our data suggest that a reduction in pco2atm occurred before the main phase of ice growth, followed by a sharp recovery to pre-transition values and then a more gradual decline. During maximum ice-sheet growth, PCO2atm was between ∼450 and ∼1,500 p.p.m.v., with a central estimate of ∼760 p.p.m.v. The ice cap survived the period of Pco2atm recovery, although possibly with some reduction in its volume, implying (as models predict11) a nonlinear response to climate forcing during melting. Overall, our results confirm the central role of declining pco2atm in the development of the Antarctic ice sheet (in broad, agreement with carbon cycle modelling12) and help to constrain mechanisms and feedbacks associated with the Earth's biggest climate switch of the past 65 Myr. ©2009 Macmillan Publishers Limited. All rights reserved.
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