Dynamics and Mechanisms of South Indian Ocean Teleconnection on the West Antarctic Sea Ice in the Cold Season

Abstract

Tropical-polar teleconnections are believed to play a key role in the observed changes in Antarctica and the Southern Ocean, which have been widely studied. Here we identify a fingerprint of the South Indian Ocean (SIO) in Antarctic sea ice concentration (SIC) in the cold season, detectable as early as May. Specifically, sea surface temperature (SST) warming in the central SIO excites a downstream wave train, inducing an anomalous cyclonic circulation over the Amundsen Sea. This, in turn, leads to increased SIC in the Amundsen Sea and decreased SIC in the eastern Bellingshausen Sea and the northern Weddell Sea via anomalous wind-driven forcing and air advection. We further reveal the dynamical processes that establish the atmospheric bridge between the SIO and polar regions. On the one hand, anomalous Rossby wave sources appear over the SIO, attributed to anomalous divergent flows induced by convective and diabatic heating anomalies. On the other hand, the equivalent barotropic response of atmospheric circulation is reinforced by the feedback of storm activities, dominated by eddy vorticity forcing. In a warming climate, climate models project SST warming in the SIO, accompanied by an increasing meridional SST gradient, suggesting that the strengthened impact of the SIO on Antarctic sea ice is likely to continue.