第七届青年地学论坛

A previous modeling study has shown that when the atmospheric activities shorter than one month are excluded, the air-sea fluxes over the Southern Ocean (SO) and hence the SO circulation are greatly affected. This study further investigated the relative contributions of atmospheric forcing at 6h-2days, 2-8days and 8days-1month time scales to the changes in air-sea fluxes, the SO circulation and Antarctic sea ice induced by excluding atmospheric activities shorter than one month. We found that the atmospheric activities at 6h-2days, 2-8days, and 8days-1month time scales contribute to the similar increase of about 30%, 60%, and 10% in wind power input and eddy kinetic energy. Similarly, the Weddell Gyre and Ross Gyre are strengthened by about 30%, 50%, and 20%. Mixed layer depth in the SO becomes more vigorous, which, combined with the increased momentum flux, leads to an increase in the Meridional Overturning Circulation by 5 Sv, 9 Sv, and 2 Sv. These results indicate more dominant contributions from atmospheric activities at 2-8days time scale for the SO circulation. However, the Antarctic sea ice change is dominated by the 6h-2days atmospheric forcing, with the atmospheric activities at this time scale causing the increases of about 25% in the total sea ice area, extent and volume. Such a significant sea ice increase is caused by cooler ocean surface and stronger sea ice transport owing to the enhanced heat loss and air-ice stress induced by the atmospheric activity shorter than 2 days. Results from this study show that 6h-2days and 2-8days atmospheric phenomena play a vital role in driving the SO circulation and Antarctic sea ice. Therefore, these high frequency atmospheric activities and their effects should be properly addressed in future studies.

Southern Ocean,Antarctic sea ice,Mitgcm,momentum flux,high-frequency atmospheric variability