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

The causes of the similar to 80 ppmv increase of atmospheric carbon dioxide (CO2) during the last glacial-interglacial climatic transition remain debated. We analyzed the parallel evolution of CO2 and its stable carbon isotopic ratio (delta(CO2)-C-13) 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 delta(CO2)-C-13 record is characterized by a W shape, with two negative delta(CO2)-C-13 excursions of 0.5 parts per thousand during Heinrich 1 and Younger Dryas events, bracketing a positive delta(CO2)-C-13 peak during the Bolling/Allerod 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 CO2 increase, with additional contributions from marine productivity changes on the initial CO2 rise and delta(CO2)-C-13 decline and from rapid vegetation buildup during the CO2 plateau of the Bolling/Allerod.