Spatial and temporal dynamics of lakes in Nam Co Basin, 1991-2011

Lakes in Tibet Plateau with little effects of human activities serve as important indicators of climate change. This study analysed remote sensing data and long term climate variables to examine the hydrological response of lakes in Nam Co Basin. The area changes of lakes were extracted by Landsat TM/ETM+ and analysed by SRTM 3 DEM. And the ICESat elevation data between 2003 and 2009 were used to observe the lake level of the Nam Co Lake. The results show that the number of new formed glacier lakes increased by 36% and the area of glacier lakes increased by 36.7% (0.97 km(2)) from 1991 to 2011. At the same time, the surface area of the Nam Co Lake expanded by 3.71% (72.64 km(2)) of the original size in 1991, with a tendency value of 3.63 km(2) per year. The lake level of the Nam Co Lake shows an increase tendency of 0.24 m per year during 2003-2009. These variations appear to be related to an increase in mean annual temperature of 0.06 A(0)C per year, and an increase in annual precipitation of 2.1 mm per year in summer in the last two decades. The increased number of lakes and increased area of glacial lakes reached a peak at an altitude of 5 500-5 600 m a.s.l.. The number of new formed glacier lakes and the area of glacier lakes tend to higher altitudes. Climate change has an important impact on the variation of the glacier lakes and the Nam Co Lake.