The response of lake-glacier variations to climate change in Nam Co Catchment, central Tibetan Plateau, during 1970-2000

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 integrated method with the support of GIS. Results show that from 1970 to 2000, lake area increased from 1942.34 km(2) to 1979.79 km(2) at a rate of 1.27 km(2)/a, while glacier area decreased from 167.62 km(2) to 141.88 km(2) at a rate of 0.86 km(2)/a. The increasing rate of lake in 1991-2000 was 1.76 km(2)/a that was faster than 1.03 km(2)/a in 1970-1991, while in the same period of time, the shrinking rates of glaciers were 0.97 km(2)/a and 0.80 km(2)/a respectively. Important factors, relevant to lake and glacier response to the climate, such as air temperature, 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 glacier melting water, increase of precipitation and obvious decrease of potential evapotranspiration. 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.