Monitoring Glacier Change Based On Remote Sensing In The Altun Mountain In The Last Four Decades

Altun region is selected as the study area.Data source is Landsat series satellites remote sensing images of1973MSS,1999ETM+and2010TM three periods.In support of the Geographic Information System, this paper used the supervised classification method and the ratio threshold method to extract the glaciers boundary of the study area.Meanwhile we combined the Glacier Inventory data with Google Earth terrain image,and corrected the glacier boundary through visual interpretation,and got relevant information of glaciers in study area.In the end,we analysised of the variation of the glacier during the recent40years; At the same time,we analyzed the temperature and precipitation characteristics of Ruoqiang,Qiemo,Mangya,Cold Lake and Dunhuang five meteorological stations around the study area in recent50years.In order to make approximate comparison, we explored the relationship of the glacier changes and climate change response in the study area; In addition, this paper used the fractal theory to analyze the spatial structure characteristics and the complexity of the glaciers in the study area,and made a preliminary forecast of the future glacier change; Finally,we analyzed the glaciers change of the study area and other parts.The main conclusions areas follows:1. Glacier Changes:In1973, the total glacier of Altun Mountains region is398,glacier area reached347.99km2,and the glacier average area is0.874km2.During the past40years, glaciers of the study area in general continued to retreat,and the area of glaciers have retreated54.22km2,area retreat rate is15.58%, average annual withdrawal rate is1.47km2·a-1,that is,0.42%·a-1,28glaciers have disappeared. In which, from1973to1999, the area of glaciers have retreated9.87%,average annual retreat rate is0.38%·a-1.During this time,11glaciers disappeared; From1999to2010, the area of glaciers retreated6.33%, average annual retreat rate is0.58%·a-1, and17glaciers have disappeared. Nearly10a, glacial retreat rate was significantly accelerated. Glacier changes vary among different regions of the study area, eastern section retreats the fastest, followed by the western part, the slowest is the middle. Rating of glaciers is inversely related to glacier area decreased percentage, That is, the smaller the glacier scales, the faster the retreat is, and the retreat is severer. The glaciers in each aspect of the study area, are retreating, glacial retreat of east slope and northern slope is the most serious, the glaciers of the southeast slope retreat least, the retreat of glaciers in other aspect extent centered2. Climate Change:Average temperature in the vicinity of the study area overall showed a warming trend in recent50years and the trend is clearly, warming rate reached0.41℃/10a Among them,maximum rate of warming is0.50℃/10a in winter, warming rate in summer and autumn is roughly equal, respectively,040/10a and0.39℃/10a,minimum warming rate is0.33℃/10a in spring; Annual rainfall fluctuations change, but less inclined to change, the annual precipitation rate of growth is2.21mm/10a,years of average rainfall is32.11mm.The maximum average annual rainfall is in summer, accounting for68.83of the average precipitation, the least average precipitation in winter, only5.14%of average precipitation. Each season precipitation was weak increasing trend.3. The influencing factors of the glacier changes:Small glaciers in the study area account for the vast majority, a large number of small glaciers is an important factor of the cause for the glacier sensitive to climate change and retreat of glacier area. Temperature significantly increased, however, precipitation changed little is the fundamental reason of the continuing retreat of the glacier. Among them, the summer temperatures significantly increased is the most important climatic factor causing the glacier retreating4. Glacier spatial structure distribution and forecast:Analysis about glacier spatial structures of the study area by fractal theory found that, there has been a certain rise for the District glacier stability index in recent40a,which shows the glacier stability index presented a weak increasing trend. Glacial melting will stabilize, however, the ablation rate will remain high.5. Compared with other parts of glacier changes and their reasons for the differences:Altun region glacier trends are consistent with other glaciers in western China reflected in the trend,that is the trend of the area of glaciers atrophy.The number of glaciers reduces and the ice deposits downward. The glacial retreat rate demonstrated the decreasing trend from the outer edge of the plateau to the plateau inland area in the Qinghai-Tibet Plateau. The retreat rate of the glaciers in eastern section of Himalayan and the Eastern Qilian is particularly high, maybe related to the former is affected more pronounced by the South Asia monsoon than other regions. While the latter is affected more significantly by the East Asian monsoon than other regions, accordingly glacier change may be more sensitive to changes in climate and environment. Glacial retreat rate in Altun region is larger than the other outer edge of the Qinghai-Tibet Plateau.That may be related with a large number of small glaciers in the region.