Variation of the Laohugou Glacier No.12 in the Qilian Mountains

The Laohugou Glacier No.12,a complex valley glacier with extreme-continental features,10.1 km in length and 21.9 km2 in area,is a large glacier in the Qilian Mountains,which attracts many glaciologists' attention for its special physical properties.The monitoring the Laohugou Glacier No.12 was begun in 1958,and ceased in 1962.Afterwards,some short-term scientific expedition to the glacier was taken in the middle of 1970s' and the 1980s.In 2005,an integrated monitoring was resumed.Based on the field observation using GPS,1∶50 000 topographic maps and the ETM+ image,Variation of the Laohugou Glacier No.12 and its response to climate in the last 50 years are analyzed.It is found that the glacier retreated 100 m from 1957 to 1976,equivalent to a retreat speed of 5 m·a-1.Afterwards,it became to be steady.Again,from 1986 to 2005,the glacier retreated 140.12 m,with a velocity 40.2% quicker than that from 1957 to 1976.Considering the climate data of Yumenzen Station,one can see that temperature rising is the major controlling factor of the glacier change during the last 20 years.It also shows that glacier is much sensitive to climate change in warm background than in cold background.