基于GIS的玛旁雍错流域冰川地貌及现代冰川湖泊变化研究

The Glacial Landforms and the Changes of Glacier and Lake Area in the Mapam Yumco Basin in Tibetan Plateau Based on GIS

基于多源多时相的数字遥感影像、地形图和DEM数据,利用遥感(RS)和地理信息系统(GIS)技术,对西藏玛旁雍错流域冰川地貌类型和空间分布进行了研究,并对流域内近30 a来冰川和湖泊的变化进行分析.结果表明:1974—2003年玛旁雍错流域冰川总面积减少了7.27 km2,平均退缩速率0.24 km2.a-1;湖泊总面积减少37.58 km2,平均退缩速率1.25 km2.a-1.多时相的监测表明,冰川在加速退缩,且阳坡冰川的消融速度大于阴坡,坡度陡、面积小的冰川消融比例大于坡度缓、面积较大的冰川;湖泊面积先减少后有所增加,但总面积还是减少了,不少小湖泊消失.分析流域附近气象资料可知,气温上升和降水量减少是玛旁雍错流域内冰川消融与退缩的主要原因.

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 km^2 , or 6.7 % of the total area with an average retreat rate of 0. 24 km^2·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 km^2 , accounting for 4.81% of the total area, and an average retreat rate of 1.25 km^2 · 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.