Bärbel Hönisch et al., Science, 324, June 19, 2009: Atmospheric carbon dioxide concentration across the mid-Pleistocene transition

Science, 19 June 2009, Vol. 324, No. 5934, pp. 1551-1554; DOI: 10.1126/science.1171477

Reports

Atmospheric carbon dioxide concentration across the mid-Pleistocene transition

Bärbel Hönisch (Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory of Columbia University, NY 10964–8000, U.S.A.), N. Gary Hemming (Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory of Columbia University, NY 10964–8000, U.S.A., and School of Earth and Environmental Sciences, Queens College, New York, NY, 11367–1597, U.S.A.), David Archer (Department of Geophysical Sciences, University of Chicago, Chicago, IL 60637, U.S.A.), Mark Siddall (Department of Earth Sciences, University of Bristol, Bristol, U.K.), and Jerry F. McManus (Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory of Columbia University, NY 10964–8000, U.S.A.)

The dominant period of Pleistocene glacial cycles changed during the mid-Pleistocene from 40,000 years to 100,000 years, for as yet unknown reasons. Here we present a 2.1-million-year record of sea surface partial pressure of CO₂ (PCO₂), based on boron isotopes in planktic foraminifer shells, which suggests that the atmospheric partial pressure of CO₂ (pCO₂) was relatively stable before the mid-Pleistocene climate transition. Glacial PCO₂ was ~31 microatmospheres higher before the transition (more than 1 million years ago), but interglacial PCO₂ was similar to that of late Pleistocene interglacial cycles (<450,000 years ago). These estimates are consistent with a close linkage between atmospheric CO₂ concentration and global climate, but the lack of a gradual decrease in interglacial PCO₂ does not support the suggestion that a long-term drawdown of atmospheric CO₂ was the main cause of the climate transition.

Link to abstract: http://www.sciencemag.org/cgi/content/abstract/324/5934/1551