Understanding Relationship between Melt/Freeze Conditions Derived from Spaceborne Scatterometer and Field Observations at Larsemann Hills, East Antarctica during Austral Summer 2015-16

Snow fork and ground penetrating radar at 200 MHz were used for snow depth, wetness and density measurements towards understanding the relationship between melt/freeze conditions derived from spaceborne Advance Scatterometer (ASCAT) and Oceansat-2 Scatterometer (OSCAT), and field observations. The observations were acquired at Larsemann Hills, East Antarctica in austral summer of 2015-16 during the 35th Indian Scientific Expedition to Antarctica. The field observations of wetness correlated well with identified dry and percolation zones showcasing different behaviours of density and wetness. Ice firn was observed at 50-55 cm depth, even in dry zone. Melt onset and number of melt days based on ASCAT varied spatially and temporally over the years and correlated well with positive degree day (PDD) for automatic weather station data located at the Indian Antarctic station, Bharati. Backscatter measurements by OSCAT showed that winter backscatter reduced with accumulation for both dry and percolation zones, but increased in the later part of winter in the percolation zone. A positive but low correlation was observed between ASCAT backscatter to accumulation and the surface mass balance from regional atmospheric climate model (RACMO2.3). A high correlation of 0.78 was observed between reduction in backscatter due to liquid water content and PDD, which coincides with field observations of wetness. The observations serve as baseline to monitor melt conditions and stability of existing ice sheet.