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Glacier Variation since the Maximum of the Little Ice Age in the Western Qilian Mountains, Northwest China

LIU Shi yin 1, SHEN Yong ping 1, SUN Wen xin 2, LI Gang 1 (1.Cold and Arid Region Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou Gansu 730000, China; 2. Institute of Remote Sensing and Applications, Ch  
Variations of global land ice are of particular interest to global change scientists and governmental authorities, which concern the effects of glacier change on worldwide sea level change, glacial related disasters in mountainous regions and water resources in arid areas. For mountainous areas like high mountains and plateaus in Central Asian, glacier melt water plays an important role in the water supply for irrigation, industrial and common life, especially, in the drought years. In this paper, a comparative analysis is performed for glacier area variation since the maximum of the Little Ice Age (LIA) in the western Qilian Mountains, Northwest China. Glacier extents in the LIA maximum and in 1956 were derived from air photos and relevant photogrammetric maps. The extent in 1990 was extracted from Landsat TM image acquired in Sept. 1990, which was geometrically corrected by coregistering to the above-mentioned maps. It is found that total glacier area in four large river basins was in average 16.9% more than that in 1956 (Table 1). The satellite image of 1990 in the north part (Daxueshan Mountains) of the western Qilian Mountains demonstrated a glacier area decrease of 4.8% compared with that in 1956. An analysis has been performed for the data of glacier inventory of the western Qilian Mountains. The analysis shows that glacier area has close relationship to ice volume, as well as to glacier length. Thus, Glacier volume and length changes between the LIA and 1956 and between 1956 and 1990 can be calculated. Calculation shows that glacier volume and length changes were about 14.1% and 11 5% (relative to the situation in 1956) from the LIA to 1956. The calculation for the Daxueshan Mountains from 1956 to 1990 was extended to the western part of the Qilian Mountains by using the derived relations. It is revealed that glacier area and volume decreased by 10 3% and 9 3% during this period, which means that there was a much stronger recession of glaciers from 1956 to 1990, and correspondingly the rivers in this region have received an extra glacial runoff of about 50×10 8 m 3.
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