A. K. Tripati, C. D. Roberts & R. A. Eagle, Science (2009): Coupling of CO2 and ice sheet stability over major climate transitions of the last 20 million years

Science, published online October 8, 2009; DOI: 10.1126/science.1178296

Reports

Coupling of CO₂ and ice sheet stability over major climate transitions of the last 20 million years

Aradhna K. Tripati ^* (Departments of Earth and Space Sciences and Atmospheric and Oceanic Sciences, and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095, U.S.A.; Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, U.K.), Christopher D. Roberts (Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, U.K.), and Robert A. Eagle (Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, U.S.A.) 

(Submitted on June 26, 2009; accepted on September 28, 2009.)

Abstract

The CO₂ content of the atmosphere has varied cyclically between ~180 and ~280 ppmv over the last 800,000 years, closely coupled with temperature and sea level. For earlier periods in Earth’s history, pCO₂ is much less certain and the relationship between pCO₂ and climate remains poorly constrained. We use boron/calcium ratios in foraminifera to estimate pCO₂ during major climate transitions of the last 20 million years (myr). During the Middle Miocene, when temperatures were ~3-6 °C warmer and sea level 25-40 meters higher than present, pCO₂ was similar to modern levels. Decreases in pCO₂ were synchronous with major episodes of glacial expansion during the Middle Miocene (~14-10 million years ago; Ma) and Late Pliocene (~3.3 to -2.4 Ma).

^*Correspondence should be addressed.  Aradhna K. Tripati, e-mail: aradhna.tripati@gmail.com

Link to abstract:  http://www.sciencemag.org/cgi/content/abstract/1178296