Constraint of the CO₂ rise by new atmospheric carbon isotopic measurements during the last deglaciation

Abstract

The causes of the ∼80 ppmv increase of atmospheric carbon dioxide (CO 2 ) during the last glacial‐interglacial climatic transition remain debated. We analyzed the parallel evolution of CO 2 and its stable carbon isotopic ratio ( δ 13 CO 2 ) in the European Project for Ice Coring in Antarctica (EPICA) Dome C ice core to bring additional constraints. Agreeing well but largely improving the Taylor Dome ice core record of lower resolution, our δ 13 CO 2 record is characterized by a W shape, with two negative δ 13 CO 2 excursions of 0.5‰ during Heinrich 1 and Younger Dryas events, bracketing a positive δ 13 CO 2 peak during the Bølling/Allerød warm period. The comparison with marine records and the outputs of two C cycle box models suggest that changes in Southern Ocean ventilation drove most of the CO 2 increase, with additional contributions from marine productivity changes on the initial CO 2 rise and δ 13 CO 2 decline and from rapid vegetation buildup during the CO 2 plateau of the Bølling/Allerød.