关键词: 玛旁雍错, 遥感, 地理信息系统, 冰川地貌, 冰川变化, 湖泊变化

Abstract: Based on remote sensing(RS) and geographical information systems(GIS) techniques,using 4 periods of data,including 1:50000 topographic maps that were published in 1974,digital images from Landsat TM in 1990,Landsat ETM+ in 1999,ASTER in 2003 and Digital Elevation Model(DEM),in this paper the glacial landforms in Mapam Yumco Basin in Tibetan Plateau are mapped,and the glacial landform area,variations of glacierized area and lakes in the past 30 years are studied.It is found that the glaciers in Mapam Yumco Basin have been retreating since 1974.In the recent years,glacier retreat is accelerated.It also shows that glacier melt rate on the sunny side is faster than those in the shadow slope,and smaller glaciers in steeper slopes melt faster than those in flat terrain.From 1974 to 2003,glacier wastage was about 7.27 km²,or 6.77% of the total area,with an average retreat rate of 0.24 km²·a^-1.Lake area was obviously in reduction in the last 30 years,shrinking from 1974 to 1999,but expanding from 1999 to 2003 to some extent.Many small lakes have disappeared.Lake shrinkage was smaller and smaller and then has shifted to lake expansion since 1999.But generally speaking,lake area was in shrinkage from 1974 to 2003,with a total area decrease of 37.58 km²,accounting for 4.81% of the total area,and an average retreat rate of 1.25 km²·a^-1.In addition,the glacier and lake variations with meteorological data during the last 30 years in the basin were analyzed.According to meteorological data from the Burang Station(with an elevation of 3 900 m a.s.l.),which is located in the southwest of Mapam Yumco basin,the average air temperature increases very obviously.Temperature increase in the Mapam Yumco basin consists with a prevailing warming over the Tibetan Plateau during the last decades.Annual precipitation and annual evaporation decreased slightly as shown in its linear fitting.The glacier retreat was most likely due to the negative glacial mass balance and was affected by rising temperature and decreasing precipitation over the Tibetan Plateau.Early lake decrease was likely to be caused by less precipitation in the basin.On the other hand,lake expansion has accelerated since 1999,which was most likely due to more water supplies from intensive melting of glaciers,in addition to less water loss due to evaporation and less precipitation income in the basin.

Key words: Mapam Yumco Basin, RS, GIS, glacial landforms, glacier change, lake change