Glacier Changes In The Lenglongling Mountain,Eastern Qilian Shan

Glaciers are a critical component of the earth system. Present accelerated melting and retreat of glaciers has severe impacts on environment and human well-being, including vegetation patterns, economic livelihood, natural disasters, and water-energy supplies. Changes of glaciers in mountainous regions are widely recognized as one of the best natural indicators of global climate change. The decline in glacier extent in mountains and other regions contributes to sea level rise. The glaciers in the west of China are not only an important supply of the numerous rivers, but also a large solid freshwater resource, which affect the life of peoples of the western dry region. Under the background of global warming, most of glaciers in China are retreating and glacier retreat has become more aggravate since1980s. Compared with the traditional single direct observation method, studies of glacier changes have involved multi data sources and multi indirect observations. The combination of remote sensing, GPS and GIS can be used to help us extract glacier changes efficiently.In this paper, the glaciers over the Lenglongling mountains in the northeastern margin of the Tibetan Plateau was investigate. Based on topographic map, satellite imagery, GPS measurement and stakes on the glacier surface, the changes of glacier area, length, elevation and ice volume are investigated. The glacial movement and ablation are discussed to investigate the glacier response to climate change. Results are summarized as followings:1) There were244glaciers Lenglongling Mountain in1972with the area of101.6km2and ice volume of3.299km3, of which220glaciers were characterized by the glacial area less than1km2. The glacial area reduced to66.7km2by2012with the retreating rate of34.4%(0.86%/a). During1972to2012, the glacial area of the western Lenglongling Mountain reduced27.5km2, accounting for31.9%of the total area in1972. The average are retreating rate was0.68km2/a (0.80%/a), but the area changing rate was different in different periods. The rate was1.28%/a during1995～1999,1.15%/a during1999～2002and reached the minimum of0.79%/a during1972～1995. The retreating rate was higher in the southern slope (1.06%/a) than in the northern slope (0.69%/a). 2) During1972～2010, the fronts of9glaciers in the Ningchan and Shuiguan watershed had retreated between91±57.4m (2.4±1.5m/a) and250±57.4m (6.6±1.5m/a) in Ningchan and Shuiguan River. The total glacier area decreased by1.2km2accounting for9.9%of the glacierized area in1972. Mean thinning rate is approximately-0.64±0.29m/a in water equivalent (w.e.) in the measurement area and the wasting ice mass is about142.6±79.3X10-3km3. The ice volume in Lenglongling Mountain has decreased by42%from1972to2012.3) The retreat of glaciers in the Lenglongling mountains were mainly resulted from the temperature rising. Though the precipitation during some period increased, the glacial accumulation cannot make up the glacier ablation caused by climate warming. Moreover, the glacier retreat were controlled by the combined impact of temperature, precipitation, the glacier size and topography, of which temperature and glacier size were the most important factors. Compared with the northern slope, the southern slope was characterized by more obvious temperature increase and smaller glacier size, leading to higher glacial area retreating rate in the northern slope.4) The mean annual mass balance of NC01glacier was-1260mm during2010～2012. The ELA was at4660m, exceeded the maximum altitude of NC01glacier, which means the whole glacier is in ablation zone.. The mean annual mass balance of SG04glacier was-808mm, ranging from-808mm to-294mm. The ELA was at4680m, rising180m since1972.5) The mean glacier velocity for NC01and SG04glacier was2.8m/a and5.2m/a, respectively during2010～2011. The results showed that the glacier velocity decreased compared with the early studies, indicating that the variation of glacier scale due to continuous glacier ablation had a major impact on the glacier velocity.6) According to the linear relationship between glacier ablation and elevation, the volume of melting water during28June～8September2012, was0.0083km3in the Xiying watershed based on degree-day model. The volume of glacial melting water accounted for3.9%of the total discharge, which would increased to4.8%assuming the temperature increased by1℃.