Varied contribution of the Southern Ocean to deglacial atmospheric CO 2 rise

• Published in: Nature Geoscience
• Main Authors: Moy, AD, Palmer, MR, Howard, WR, Bijma, J, Cooper, MJ, Calvo, E, Pelejero, C, Gagan, MK, Chalk, TB
• Format: Article in Journal/Newspaper
• Language: English
• Published: Nature Publishing Group 2019
• Subjects: Earth Sciences; Physical Geography and Environmental Geoscience; Palaeoclimatology; Antarctic; Southern Ocean; Antarc*; Planktonic foraminifera
• Online Access: https://doi.org/10.1038/s41561-019-0473-9; http://ecite.utas.edu.au/135550

Glacialinterglacial changes in atmospheric CO 2 are generally attributed to changes in seawater carbon chemistry in response to large-scale shifts in the oceans biogeochemistry and general circulation. The Southern Ocean currently takes up more CO 2 than any other and it is likely to have played a crucial role in regulating past atmospheric CO 2 . However, the physical, biological and chemical variables that control oceanatmosphere CO 2 exchange during glacialinterglacial 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 2 partial pressure in sub-Antarctic surface waters south of Tasmania over the past 25,000 years, and investigate the mechanisms that regulate seawater CO 2 . The new record shows that surface waters in this region were a sink for atmospheric CO 2 during the Last Glacial Maximum. Our reconstruction suggests changes in the strength of the biological pump and the release of deep-ocean CO 2 to surface waters contributed to the last deglacial rise in atmospheric CO 2 . 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 2 during the last glacialinterglacial cycle.