Abstract
The Southern Ocean is known to play an important role in the global climate system, because the Antarctic cryosphere represents the largest accumulation of ice on the Earth's surface. The latitudinal migration of the oceanic fronts and sea-ice coverage in the Southern Ocean should have an influence on the surface water circulation, as well as primary productivity, heat transport, and temperature gradient. Recent paleoceanographic studies on deep sea sediments from the Southern Ocean have demonstrated the latitudinal migration of the Subtropical Convergence (STC) and Antarctic Polar Front (APF) during the glacial/interglacial cycles and the larger drop in sea surface temperatures (SST) than SST change estimation by the CLIMAP project. Paleoproductivity in the Subantarctic Southern Ocean, which is north of the present APF, increased during the glacials due to a northward shift of the circum-Antarctic biogenic silica belt and an enhanced dust input. On the other hand, the surface water south of the APF was presumably stratified due to extended sea ice coverage. The stratification of the Antarctic surface water blocked CO2 emission from the intermediate and deep waters to the atmosphere. Variations in the biological pump and stratification in the Southern Ocean surface water and its associated drawdown of atmospheric CO2 have been proposed as a forcing mechanism for the global climate changes.
