Carbon isotope records reveal precise timing of enhanced Southern Ocean upwelling during the last deglaciation.

The Southern Ocean plays a prominent role in the Earth's climate and carbon cycle. Changes in the Southern Ocean circulation may have regulated the release of CO2 to the atmosphere from a deep-ocean reservoir during the last deglaciation. However, the path and exact timing of this deglacial CO2 release are still under debate. Here we present measurements of deglacial surface reservoir ¹4C age changes in the eastern Pacific sector of the Southern Ocean, obtained by ¹4C dating of tephra deposited over the marine and terrestrial regions. These results, along with records of foraminifera benthic-planktic ¹4C age and δ¹³C difference, provide evidence for three periods of enhanced upwelling in the Southern Ocean during the last deglaciation, supporting the hypothesis that Southern Ocean upwelling contributed to the deglacial rise in atmospheric CO2. These independently dated marine records suggest synchronous changes in the Southern Ocean circulation and Antarctic climate during the last deglaciation.