Varied contribution of the Southern Ocean to deglacial atmospheric CO2 rise

• Published in: Nature Geoscience
• Main Authors: Moy, Andrew D., Palmer, Martin R., Howard, William R., Bijma, Jelle, Cooper, Matthew J., Calvo, Eva, Pelejero, Carles, Gagan, Michael K., Chalk, Thomas B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Nature Publishing Group 2019
• Subjects: General Earth and Planetary Sciences; 1900 Earth and Planetary Sciences; Antarctic; Southern Ocean; Antarc*; Planktonic foraminifera
• Online Access: https://espace.library.uq.edu.au/view/UQ:edbeed7/UQedbeed7_OA.pdf; https://espace.library.uq.edu.au/view/UQ:edbeed7

Glacial–interglacial changes in atmospheric CO are generally attributed to changes in seawater carbon chemistry in response to large-scale shifts in the ocean’s biogeochemistry and general circulation. The Southern Ocean currently takes up more CO than any other and it is likely to have played a crucial role in regulating past atmospheric CO. However, the physical, biological and chemical variables that control ocean–atmosphere CO exchange during glacial–interglacial cycles are not completely understood. Here we use boron isotopes and carbon isotopes in planktonic foraminifera and an alkenone-based proxy of temperature to reconstruct seawater pH and CO partial pressure in sub-Antarctic surface waters south of Tasmania over the past 25,000 years, and investigate the mechanisms that regulate seawater CO. The new record shows that surface waters in this region were a sink for atmospheric CO during the Last Glacial Maximum. Our reconstruction suggests changes in the strength of the biological pump and the release of deep-ocean CO to surface waters contributed to the last deglacial rise in atmospheric CO. These findings demonstrate that variations in upwelling intensity and the distribution of Southern Ocean water masses in this sector played a key role in regulating atmospheric CO during the last glacial–interglacial cycle.