Glacier changes in Youyi Area in the Altay Mountains of Xinjiang during 1959-2008

Research on glacier change has been limited in Chinese Altay Mountains among the border of China,Russia and Mongolia,despite the fact that the number of glaciers in the Altay Mountains is less among all mountain ranges in China,and the glaciers in this region provide very important water resources for local economic development and drinking water for man use.Most of the research on glaciers in China is in Tianshan Mountains,Qinghai-Tibet Plateau and Qilian Mountains,but not in Altay Mountains.During the past several decades,most glaciers are in a state of rapid retreating due to climate warming.The glaciers of Youyi in the Altay Mountains were selected as the study area.Based on 1∶50 000 topographic maps in 1959,ASTER remote sensing data in 2008 and digital elevation model(DEM),the study area for glaciers was extracted by using the remote sensing image processing and analyzing method,and the changes of glaciers in the study area were analyzed under the support of the geographic information systems technology.The results indicate that the amplitude of the whole change of glaciers in the Youyi Area is large and glaciers in this area have retreated rapidly during the study period from 1959 to 2008.In the study period,the total area and number of the investigated glaciers(226) have reduced by 32.5%and 27.9%.At the same time,the results showed that glaciers average rate of change with area less than 1 km2 is-66.7% and glaciers average rate of change with area less than 0.5 km2 is-70%.Moreover,those glaciers with area from 1 to 5 km2 have reduced by 27.9%.The paper analyzed the reasons of the large change rate of glaciers,and the results indicate that the large change rate of glaciers is caused by the large proportion of small glaciers,whose glaciers smaller than 1 km2 account for nearly 75% in the investigated glaciers.Moreover,the results show that the larger the glaciers are,the higher the amplitude of the ablation is,but the reduced rate is lower.And those glaciers have the highest degree of response to climate change.The glaciers retreated by 253 m at a rate of 18.3%.The glacier changes exhibited obvious spatial differences,indicating that the reduction rate of glaciers to the south slope of the Youyi Area was larger than that of the north.