Glacier shrinkage in the Daxue and Danghenan ranges of the western Qilian Mountains, China, from 1957 to 2010

Changes in glaciers in the Daxue and Danghenan ranges were analyzed based on topographic maps, satellite images and a digital elevation model (DEM). The results indicate that from 1957/1966 to 2010, the total area and ice volume for the investigated glaciers declined by 17.21 and 24.10 % in these respective ranges. From 1957 to 2010, the total area and ice volume in the glaciers in the Daxue Range declined by 16.03 % (0.30 % a−1) and 22.40 %, respectively, with a mean reduction of 0.133 km2 for an individual glacier. These glaciers retreated by an average of 258 m (3.4 m a−1). From 1966 to 2010, the total area and ice volume for the glaciers in the Danghenan Range declined by 18.32 % (0.42 % a−1) and 25.70 %, with a mean reduction of 0.111 km2 for an individual glacier. These glaciers retreated by an average of 159 m (3.6 m a−1). The rate of glacier retreat on the south-facing slopes was faster than that on the north-facing slopes. The area of glaciers on the south and north slopes of the Daxue Range declined by 22.82 and 15.51 %, respectively, and the area of glaciers on the south and north slopes of the Danghenan Range declined by 22.39 and 16.76 %, respectively. An analysis of the general trend of climatic change in the study area revealed that rapidly rising air temperatures were most likely the major factor causing the loss of glacier ice within the study area. Compared with other glaciers in the eastern and middle Qilian Mountains, glaciers in the western Qilian Mountains appeared to be losing mass at a slower rate. The differences of glacier changes in the eastern, middle, and western Qilian Mountains are mainly caused by the combination of climatic conditions and glacier morphologic factors.