Vertical profile of the specific surface area and density of the snow at Dome C and on a transect to Dumont D'Urville, Antarctica - albedo calculations and comparison to remote sensing products

International audienceThe specific surface area (SSA) of snow determines in part the albedo of snow surfaces and the capacity of the snow to adsorb chemical species and catalyze reactions. Despite these crucial roles, almost no value of snow SSA are available for the largest permanent snow expanse on Earth, the Antarctic. We report the first extensive study of vertical profiles of snow SSA near Dome C (DC: 75 060 S, 123 200 E, 3233ma.s.l.) on the Antarctic plateau, and at seven sites during the logistical traverse between Dome C and the French coastal base Dumont D'Urville (DDU: 66 400 S, 140 010 E) during the Austral summer 2008-2009. We used the DUFISSS system, which measures the IR reflectance of snow at 1310 nm with an integrating sphere. At DC, the mean SSA of the snow in the top 1 cm is 38m2 kg−1, decreasing monotonically to 14m2 kg−1 at a depth of 50 cm. Along the traverse, the snow SSA profile is similar to that at DC in the first 600 km from DC. Closer to DDU, the SSA of the top 5 cm is 23m2 kg−1, decreasing to 19m2 kg−1 at 50 cm depth. This difference is attributed to wind, which causes a rapid decrease of surface snow SSA, but forms hard windpacks whose SSA decrease more slowly with time. Since light-absorbing impurities are not concentrated enough to affect albedo, the vertical profiles of SSA and density were used to calculate the spectral albedo of the snow for several realistic illumination conditions, using the DISORT radiative transfer model. A preliminary comparison with MODIS data is presented and our calculations and MODIS data show similar trends