Carbon Isotope Constraints on the Deglacial CO2 Rise from Ice Cores

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Science  29 Mar 2012:
DOI: 10.1126/science.1217161

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The stable carbon isotope ratio of atmospheric CO213Catm) is a key parameter to decipher past carbon cycle changes. Here, we present δ13Catm data for the last 24,000 years derived from three Antarctic ice cores. We conclude that a pronounced 0.3‰ decrease in δ13Catm during the early deglaciation can be best explained by upwelling of old, carbon-enriched waters in the Southern Ocean. Later in the deglaciation, regrowth of the terrestrial biosphere, changes in sea surface temperature, and ocean circulation governed the δ13Catm evolution. During the Last Glacial Maximum, δ13Catm and CO2 were essentially constant, suggesting that the carbon cycle was in dynamic equilibrium and that the net transfer of carbon to the deep ocean had occurred before then.

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