Impact of air-sea forcings on the southern ocean sea ice variability around the Indian Antarctic stations

Abstract

A coupled ocean sea ice model is used to carry out sensitivity experiments to decipher the respective roles of wind, heat and freshwater flux forcings in changing the sea ice variability (concentration, volume, salinity, and drift speed) of the Antarctic region with special emphasis near the Indian Stations, Maitri [11.7°E; 70.7°S] and Bharati [76.1°E; 69.4°S]. The simulations are carried out in the Southern Ocean region [9°E−78°E; 58°S-71°S] during 1997–2012 at a resolution of 6–10 km. It is found that the air-sea forcings greatly impact the spatio-temporal variability of the sea ice variables. In the absence of wind and heat/freshwater flux forcing, the sea ice concentration (SIC) and sea ice volume (SIV) of the region decreases, except at higher latitudes. The effect of absence of heat and freshwater flux forcing on the seasonal variability of the SIC and SIV is more as compared to the wind forcing. Interestingly, the absence of wind and heat flux forcing exhibit opposite nature in influencing the temporal variability of SIV around the Maitri and Bharati regions. On using the climatological wind and heat/freshwater flux forcing, the SIC and SIV of the region increases. The climatological wind forcing have a greater effect in increasing the SIC and SIV of the region as compared to corresponding heat and freshwater flux forcings. The highest contribution in the SIV comes from the thick ice. The SIV of thick ice is found to be significantly increasing (4% per year). However, the interannual increase in medium thick ice and thin ice is very small (0.1% per year). The changes in the sea ice drift speed and vertical stability of ocean is studied vis-à-vis changes in air-sea forcing. The mixed layer heat budget of the region is also estimated and the effect of wind and heat flux forcing on it is investigated.