NOAA NCDC National Climatic Data Center
NOAA Paleoclimatology Program, NCDC Paleoclimatology Branch  
Paleoclimatology Navigation Bar Bookmark and Share
NOAA National Environmental Satellite, Data, and Information Service National Oceanic and Atmospheric Administration NOAA National Climatic Data Center U.S. Department of Commerce Paleo Home Data Paleo Projects Paleo Perspectives Education and Outreach About Paleo Program Site Map

Atmospheric carbon dioxide through the Eocene-Oligocene climate transition

Satellite image of Antarctica.  NASA/Goddard Space Flight Center, Scientific Visualization Studio

Atmospheric carbon dioxide through the Eocene-Oligocene climate transition

Vol. 461, pp. 1110-1113, 22 October 2009

Paul N. Pearson1, Gavin L. Foster2, and Bridget S. Wade3
1 School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3YE, UK
2 Bristol Isotope Group, Department of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK
3 Department of Geology and Geophysics, Texas A&M University, College Station, Texas 77843-3115, USA
Geological and geochemical evidence indicates that the Antarctic ice sheet formed during the Eocene-Oligocene transition, 33.5-34.0 million years ago. Modelling studies suggest that such ice-sheet formation might have been triggered when atmospheric carbon dioxide levels (P CO2atm) fell below a critical threshold of 750 p.p.m.v., but the timing and magnitude of P CO2atm relative to the evolution of the ice sheet has remained unclear. Here we use the boron isotope pH proxy on exceptionally well-preserved carbonate microfossils from a recently discovered geological section in Tanzania to estimate P CO2atm before, during and after the climate transition. Our data suggest that a reduction in P CO2atm 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, P CO2atm 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 P CO2atm recovery, although possibly with some reduction in its volume, implying (as models predict) a nonlinear response to climate forcing during melting. Overall, our results confirm the central role of declining P CO2atm in the development of the Antarctic ice sheet (in broad agreement with carbon cycle modelling) and help to constrain mechanisms and feedbacks associated with the Earth's biggest climate switch of the past 65 Myr.
Download data from the WDC Paleo archive:
Tanzania Eocene-Oligocene δ11B Data and P CO2atm Reconstruction Text or Excel format.

To read or view the full study, please visit the Nature website.
It was published in Nature, Vol. 461, pp. 1110-1113, 22 October 2009
Dividing Line
Privacy Policy information Open Access Climate Data Policy link USA logo Disclaimer information
Dividing Line
Downloaded Sunday, 01-Feb-2015 10:05:01 EST
Last Updated Friday, 13-Nov-2009 08:18:04 EST by
Please see the Paleoclimatology Contact Page or the NCDC Contact Page if you have questions or comments.