Atmospheric Carbon Dioxide Concentration Across the Mid-Pleistocene Transition
2009
Hönisch, Bärbel | Hemming, N Gary | Archer, David | Siddall, Mark | McManus, Jerry F.
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 approximately 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.
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