Varied contribution of the Southern Ocean to deglacial atmospheric CO2 rise

Here we use oxygen, carbon and boron isotopes, and planktonic foraminiferal shell weights in planktonic foraminifera and an alkenone-based proxy of temperature to reconstruct seawater pH and CO2 partial pressure in sub-Antarctic surface waters south of Tasmania over the past 25,000 years Glacial–interglacial changes in atmospheric CO2 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 CO2 than any other and it is likely to have played a crucial role in regulating past atmospheric CO2. However, the physical, biological and chemical variables that control ocean–atmosphere CO2 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 the seawater pH and CO2 partial pressure in sub-Antarctic surface waters south of Tasmania over the past 25,000 years, and investigate the mechanisms that regulate seawater CO2.