Atmospheric CO 2 and Climate on Millennial Time Scales During the Last Glacial Period

Abstract

Reconstructions of ancient atmospheric carbon dioxide (CO 2 ) variations help us better understand how the global carbon cycle and climate are linked. We compared CO 2 variations on millennial time scales between 20,000 and 90,000 years ago with an Antarctic temperature proxy and records of abrupt climate change in the Northern Hemisphere. CO 2 concentration and Antarctic temperature were positively correlated over millennial-scale climate cycles, implying a strong connection to Southern Ocean processes. Evidence from marine sediment proxies indicates that CO 2 concentration rose most rapidly when North Atlantic Deep Water shoaled and stratification in the Southern Ocean was reduced. These increases in CO 2 concentration occurred during stadial (cold) periods in the Northern Hemisphere, several thousand years before abrupt warming events in Greenland.