GLACIOLOGICAL STUDIES ON NELSON ISLAND, SOUTH-SHETLAND ISLANDS, ANTARCTICA

The ice cap on Nelson Island in the South Shetland Islands, West Antar ctica, was studied between 1985 and 1989. The ice cap has an average t hickness of 120 m, it is temperate, exists under the sub-Antarctic mar itime climate and almost completely covers the island. Owing to intens e percolation of meltwater land, to some extent, liquid precipitation, the snow-firn layer is in the soaked facies with a firn-ice transitio n at a depth of 25-26 m at the summit. A force-balance model suggests that the ice is almost linearly viscous but has a high viscosity. The model further suggests that basal sliding makes a larger contribution to tile ice movement than does ice deformation. From 1970 to 1988, the average accumulation rate was 120 kg m(-2) a(-1) at the centre, and b etween 1985 and 1989 the equilibrium-line elevation averaged 110 m a.s .l. Analysis of chemical impurities in the surface snow suggests that the precipitation source is mainly local marine air masses find that h uman activity has already exerted a detectable influence on the local environment.