近30年来西藏那曲地区湖泊变化对气候波动的响应

The Response of Lake Area Change to Climate Variations in North Tibetan Plateau during Last 30 Years

根据1975年地形图、20世纪80年代至2005年的TM、CBERS卫星遥感资料和近45年的气温、降水量、蒸发量、最大积雪深度和最大冻土深度等气候资料分析得出,西藏那曲地区东南部的巴木错、蓬错、东错、乃日平错等四个湖泊的水位面积在近30年来呈较显著的扩大趋势,2005年与1975年相比,分别增加了48.2km2、38.2km2、19.8km2(比2004年)、26.0km2,增长幅度分别为25.6%、28.2%、16.2%、37.6%。其主要原因与该地区近年来气温的上升、降水量的增加和蒸发量的减少、冻土退化等暖湿化的气候变化有很大关系。

Inland lake is a sensitive indicator of climate change. Because lakes in high mountain region are in natural status and are little affected by human activities, their changes can reflect climate conditions. In this paper, four inland lakes （Bamucuo, Pengcuo, Dongcuo and Nairipingcuo） area changes in area and factors causing the water level growth are analyzed using remote sensing data and climate data from meteorological stations near the four lakes. For lake area changes from 1980 to 2005, the TM and CBERS remotely sensed data and topographic map at 1：100,000 scale in 1975 are used in this study. The meteorological data including temperature, rainfall, evaporation （1971-2004）, snow depth and land frost depth from four meteorological stations Naqu, Anduo, Bange and Dangxiong which are the closest to the four lakes are used in this study. Based on the lake area information derived from a digitized 1：100,000 scale topographic map in 1975 and satellite remote sensing data from 1980 to 2005 georeferenced using topographic map, it is found out that four lakes＇ areas increased in 1980 compared with 1975, by 9.8 km^2, 9.7 km^2, 12.9 km^2 and 3.9 km^2, respectively. In 1988, the four lakes retreated and their areas are equivalent to the areas in 1975. The areas of Bamucuo, Pengcuo, Dongcuo and Nairipingcuo notably increased during the last 30 years from 1975 to 2005. Their areas increased by 48.2 km^2 （25.6%）, 38.2 km^2 （28.2%）, 19.8 km^2 （16.2%） （compared with 2004） and 26.0 km^2 （37.6%）. The lake area increase has been more obvious since 2000. The analysis of climate changes for the last 40 years shows that annual mean temperature and precipitation increased significantly, while evaporation, maximum land frost depth and maximum snow depth decreased. For instance, the mean temperature increased by 0.28℃/10a from 1961 to 2004; rainfall witnessed a big fluctuation from 1961 to 1994 and the maximum and minimum rainfall occurred in this period. The rainfall has been increasing since 1994. Evaporation decreased by 130 mm/10a from 1995 to 2004. The maximum land frost depth reduced 10 to 40 cm and the maximum snow depth decreased as well. ＂the result based on the relationship between lake area changes and climate variation shows the main factors which are directly related to lake water level are rainfall, ice snow defrost and land frost. The indirect factors of lake area changes are temperature, lake size, catchment＇s area, land formation of lake basin, surface features etc.