Mechanism of sea-ice expansion in the Indian Ocean sector of Antarctica: Insights from satellite observation and model reanalysis

In the backdrop of global warming, Antarctic sea-ice variability showed an overall expansion with the regional heterogeneity of increasing and decreasing patterns. Analysis of satellite derived sea-ice extent, during 1979 to 2015, in the Indian Ocean sector of Antarctica (IOA) revealed expansion of 2.4±1.2% decade-1. We find strengthening of westerly wind during the austral summer (between 50°S to 62°S) facilitated northward advection of a cool and fresh layer. Also, the strong westerly wind cools the upper ocean due to net heat loss from the ocean surface. The combined effect of northward advection of cold fresh layer and net heat loss from the surface, favours sea-ice expansion in the subsequent seasons, in the IOA region, north of 62°S. However, sea-ice retreat was observed near the Kerguelen Plateau, due to upper ocean warming, and hence a non-annular pattern of sea-ice extent in the IOA was observed.