Glacier InventoryGlacier changes in the Qilian Mountains in the past half-century: Based on the revised First and Second Chinese Glacier Inventory

Glaciers are the most important fresh-water resources in arid and semi-arid regions of western China. According to the Second Chinese Glacier Inventory （SCGI）, primarily compiled from Landsat TM/ETM＋ images, the Qilian Mountains had 2684 glaciers covering an area of 1597.81＋70.30 km2 and an ice volume of -84.48 km3 from 2005 to 2010. While most glaciers are small （85.66% are 〈1.0 km2）, some larger ones （12.74% in the range 1.0-5.0 km2） cover 42.44% of the total glacier area. The Laohugou Glacier No.12 （20.42 km2） located on the north slope of the Daxue Range is the only glacier 〉20 km2 in the Qilian Mountains. Median glacier elevation was 4972.7 m and gradually increased from east to west Glaciers in the Qilian Mountains are distributed in Gansu and Qinghai provinces, which have 1492 glaciers （760.96 km2） and 1192 glaciers （836.85 km2）, respectively. The Shule River basin contains the most glaciers in both area and volume. However, the Heihe River, the second largest inland river in China, has the minimum average glacier area. A comparison of glaciers from the SCGI and revised glacier inventory based on topographic maps and aerial photos taken from 1956 to 1983 indicate that all glaciers have receded, which is consistent with other mountain and plateau areas in western China. In the past half-century, the area and volume of glaciers decreased by 420.81 km2 （-20.88%） and 21.63 km3 （-20.26%）, re- spectively. Glaciers with areas 〈1.0 km2 decreased the most in number and area recession. Due to glacier shrinkage, glaciers below 4000 m completely disappeared. Glacier changes in the Qilian Mountains presented a clear longitudinal zonality, i.e., the glaciers rapidly shrank in the east but slowly in the central-west. The primary cause of glacier recession was warming temperatures, which was slightly mitigated with increased precipitation.