Glacier Variations In The Qilian Mountains,Northwest China,Between 1960S And 2015

The water tower effect in mountain areas has been a hot issue in the study of global change in recent years,and the water tower in Qinghai-Tibet Plateau,core area of high mountains in Asia is considered to be one of the most important and most threatened areas.With the background of global warming,accelerated melting and glacier retreat are widely characteristic over the past decades and have intensified in recent ten years.Located in the arid and semiarid regions of northwestern China,the Qilian Mountains are the pivotal area for the construction of the Silk Road Economic Belt in China,which is of great significance for runoff recharge in the Hexi Corridor.Therefore,it is imperative to reveal the spatiotemporal pattern of glacier changes and possible climatic drives in the Qilian Mountains,which is of great scientific value for studying the response of glaciers to climate change,but also of great practical significance to the socio-economic development of Hexi Corridor area.Based on the satellite images,Chinese glacier inventory,digital elevation data and climatic data,this paper discusses the distribution and change characteristics of glaciers in the Qilian Mountains from 1960s to 2015,changes of glacier mass balance from 2000 to 2014,regional patterns of glacier changes in typical glacierized regions,and the response of glaciers to climate change.The main conclusions are as follows:?1?Using the Landsat OLI images acquired in 2015,combined with Chinese glacier inventory and SRTM,the modern glacial changes in the Qilian Mountains from 1960s to 2015were analyzed.The result showed that there were a total of 2685 glaciers in the Qilian Mountains in 2015,with a total area of 1536.93±49.44 km²,mainly distributed in the 2-5 area class,4700-5300 elevation range and the north-facing aspect.During 1960s to 2015,the glacier shrank 397.51±116.87 km² with the retreating rate of 0.37±0.11%/a,and 109 glaciers with an area of 8.94 km² disappeared,meanwhile the shrinkage accelerated in recent ten years.The rate of relative glacier area change decreased with increasing area class and elevation,while the north-facing glacier had the largest shrinkage?164.97 km²?.There was also an accelerated trend of relative area change rate from west to east,while glaciers in the Datong River basin,located in the eastern part of mountains,shrank fastest?0.99%/a?.?2?We compared the 2000 SRTM and 2014s Tan DEM,combined with Chinese second glacier inventory,for calculating mass budgets of glaciers in the Qilian Mountains based on the geodetic method.During 2000-2014,glaciers were losing mass with an elevation decreasing rate 0.44±0.02 m a^-1,amounting to 0.37±0.03 m w.e.a^-1.The change rate of glacier surface elevation increased with decreasing elevation,to a maximum value(0.89±0.01 m a^-1)at the<4500 elevation.Consistent with the spatial pattern of glacier area changes,there was also an acceleration trend from west to east,then the maximum mass loss still occurred in the eastern region(0.65±0.05 m w.e.a^-1)and the Shiyang River basin(0.63±0.06 m w.e.a^-1).?3?The glacierized area in the Qilian Mountains was divided into seven typical glacier regions,according to the terrain development,then glacier length distribution and change characteristics were analyzed.Between 1960s to 2015,there were 702 glaciers without splitting and merging,with a total area of 563.45 km²,and an average length of 1.16 km.The average length change rates of glaciers in the typical glacier regions were-2.50 m/a and-5.27 m/a,respectively in 1960s-2007 and 2007-2015.The change rate of glacier length decreased with increasing area class,while accelerating in the past ten years.The<0.1 km² glaciers retreated fastest,and the largest average retreat rate?4.82 m/a?occurred in the glaciers of 5-10 km².The Lenglongling?region VII?showed the strongest glacial shrinkage,at 0.72 km²/a in area,6.16m/a in length from 1960s to 2015,and 0.63 m w.e.a^-1 in mass loss during 2000-2014.?4?We analyzed the relationship between glacier variation and climate change in regional scale in the Qilian Mountains.The temperature in the mountains increased dramatically and precipitation grew slightly since 1960,therefore,the continuous increase in temperature was the dominant reason of glacier shrinkage between 1960s to 2015.On the regions scale,rates of glacier shrinkage and mass loss in the western Qilian Mountains were still significantly smaller than those in the middle and east section,while mean summer temperature in west displayed more marked increasing tendency,and precipitation grew less significantly than those in other two sides.This may be related to the larger glacier size,higher average and terminal elevation of glaciers in western section.