Summary
Microwave backscatter from the Antarctic snow cover depends on the surface roughness, properties and structure within the snow cover, and moisture content. Small increases in moisture content produce a significant reduction in backscatter. This acts as a sensitive indicator of the occurrence of snow melt conditions. The ERS wind scatterometers provide an almost continuous sequence of observations of microwave backscatter coefficients over Antarctica north of latitude 79°S since August 1991. Normalised values of the backscatter coefficient are calculated by removing the anisotropic contributions, mainly from a dependence on incidence angle. Depression of these values below a long term dry snow average indicates occurrence of snow melt. The results show a large variability between summer seasons of melt extent and duration. There was very extensive and intense melting in 1991-92, with much less melt in following seasons probably in response to a cooling following the Pinatubo eruption. 1997-98 has extensive melt with a total area approaching that for 1991-92.