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Science. 2016 Sep 23;353(6306):1427-1430.

A Pleistocene ice core record of atmospheric O2 concentrations.

Author information

1
Department of Geosciences, Princeton University, Princeton, NJ 08544, USA.
2
Department of Geosciences, Princeton University, Princeton, NJ 08544, USA. Institute of Oceanology, Shanghai Jiao Tong University, Shanghai 200240, China.
3
Department of Geosciences, Princeton University, Princeton, NJ 08544, USA. Laboratoire des Sciences du Climat et de l'Environnement, Gif-sur-Yvettte, France.

Abstract

The history of atmospheric O2 partial pressures (Po2) is inextricably linked to the coevolution of life and Earth's biogeochemical cycles. Reconstructions of past Po2 rely on models and proxies but often markedly disagree. We present a record of Po2 reconstructed using O2/N2 ratios from ancient air trapped in ice. This record indicates that Po2 declined by 7 per mil (0.7%) over the past 800,000 years, requiring that O2 sinks were ~2% larger than sources. This decline is consistent with changes in burial and weathering fluxes of organic carbon and pyrite driven by either Neogene cooling or increasing Pleistocene erosion rates. The 800,000-year record of steady average carbon dioxide partial pressures (Pco2) but declining Po2 provides distinctive evidence that a silicate weathering feedback stabilizes Pco2 on million-year time scales.

PMID:
27708037
DOI:
10.1126/science.aaf5445
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