Low microwave brightness temperatures in central Antarctica: observed features and implications

Author: Surdyk, Sylviane

Source: Annals of Glaciology, Volume 34, Number 1, 1 January 2002 , pp. 134-140(7)

Publisher: International Glaciological Society

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Abstract:

The microwave brightness temperature of the ice sheet in Antarctica has a few narrow, elongated features of very low microwave brightness temperatures. The contrast inside and outside of these areas is at least 10K at 37 GHz. These features are persistent throughout the year and from year to year and occur at 6.6, 10.7, 18 and 37 GHz. The exceptionally large frequency gradients observed in this narrow area suggest that very large snow grains exist in the snow cover. Past traverse data revealed that the entire surrounding region undergoes large temperature gradients that drive high sublimation causing very large snow grains to form and the formation of both surface and depth hoar. A detailed study of former snow pits showed that, at the place of the unique features, the snow grains from the surface down to the first 2 m are the largest observed over the region. A digital elevation model shows the surface is nearly flat, and corresponds to a subglacial depression in the underlying bed. Previously reported kilometer-scale snow dunes are observed up- and downslope of the level area, but not within the level area, where the brightness temperature is lowest. In this katabatic zone, the drift-snow redistribution and the natural wind-shadow induced by the slope depression create a protected area where the snow grains can grow into very large grains.

Document Type: Research article

DOI: 10.3189/172756402781817464