A Pleistocene ice core record of atmospheric O2 concentrations

Publication Year
2016

Type

Journal Article
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. Copyright © 2016 by the American Association for the Advancement of Science; all rights reserved.
Journal
Science
Volume
353
Pages
1427-1430