Abstract:

Based upon the 1970 aero-photo topographic map, and TM/ETM satellite images taken in 1991 and 2000, the authors artificially interpreted boundaries of lake and glaciers in Nam Co Catchment, and quantified lake-glacier area variations in different stages by “inte-grated method” with the support of GIS. Results show that from 1970 to 2000, lake area in-creased from 1942.34 km² to 1979.79 km² at a rate of 1.27 km²/a, while glacier area de-creased from 167.62 km² to 141.88 km² at a rate of 0.86 km²/a. The increasing rate of lake in 1991–2000 was 1.76 km²/a that was faster than 1.03 km²/a in 1970–1991, while in the same period of time, the shrinking rates of glaciers were 0.97 km²/a and 0.80 km²/a respectively. Important factors, relevant to lake and glacier response to the climate, such as air tempera-ture, precipitation, potential evapotranspiration and their values in warm and cold seasons, were discussed. The result suggests that temperature increasing is the main reason for the accelerated melting of glaciers. Lake expansion is mainly induced by the increase of the gla-cier melting water, increase of precipitation and obvious decrease of potential evapotranspi-ration. Precipitation, evaporation and their linkages with lake enlargement on regional scale need to be thoroughly studied under the background of global warming and glacier retreating.

Key words: Tibetan Plateau, Nam Co Catchment, lake, glacier, remote sensing