Variation And Implication Of Glaciers Based On Multi-source Remote Sensing Data In Central Himalaya

High mountains in glaciation zone are especially susceptible to climate change. In recent decades, the continuous shrinkage of glaciers causes the expansion of glacial lakes and consequently results in glacial lake outburst flood/landslides and other glacial disasters in Himalayas. Such disasters have seriously threat the regional ecology and environment and the safety of life and property of local residents. Therefore, it is urgent to carry out a comprehensive study of glacier variations in this region.Dense huge mountains provide favorable terrain conditions for growth of glaciers and glacial lakes, since the center of last century, detailed study of some typical glaciers in Himalayan have been made throughout the world, but more detailed comprehensive investigation of a wide range of glaciers is scarce because of the inaccessibility of the terrain and the difficulties in field work. The emergence of new technologies of remote sensing provides more diverse and more effective means for monitoring variation of glacier system and glacial disasters. In this paper, the glaciers area, glacier length, ice surface elevation, ice volume and velocity of glacier surface and other aspects of the glaciers variations in central Himalayas were detailed analyzed and studied, based on multi-source data including topographic map, DEM elevation data, Landsat TM/ETM+, ALOS/PRISM and SAR images, combined with GIS technology. In addition, in-depth analysis of factors affecting the velocity of glaciers and the response of glaciers variations to climate change were made in consider of regional climate and local conditions of glaciers(moraine-cover, glacier surface slope, moraine lake) as well as achievement of previous studies. By the end of this study, we preliminary come to the following conclusions:1) Up to 2010, the glacier area seems to decrease overall in the study area in the past 30 years. Glacier retreat rate was 0.18%-0.20%/a. Discrepancy appears in glacier retreat rate for different size of glaciers, smaller glaciers retreat faster than the larger ones. Affected by debris-covers, moraine lakes and other factors, glacier length retreat more significantly than glacier area. Furthermore, glacier retreat rate in Everest region is less than in other regions in central Himalayas.2) Elevation changes of glacier were estimated using DEMs at different periods, and the results showed that the glacier ice thickness was reduced throughout the study area. The thinning rate is insignificant between different types of glaciers. In the Everest region, 176 of the studied glaciers were thinned at an average rate of 1.0 m/a. Besides, volume of typical glaciers was reduced, the No. 57-l glacier has lost 1.16 km3 mass in the past 30 years.3) Glacier surface velocity was extracted in the Everest region and the Lonbasaba region, based on ALOS/PALSAR and Envisat/ASAR data with feature-tracking method. From 2003 to 2010, for the 39 glaciers whose area is >5km2, in general, glacier velocity in the upper part of a glacier is faster, in some accumulation zone the velocity was reaching up to more than 100cm/d, however, velocity in ablation area is mostly less than 40cm/d. On average, non-debris covered glaciers(15.2 cm/d) move 2.2 times faster than debris covered glaciers(6.8 cm/d). Affected by debris-covers, glacier slope, glacial lakes and other local factors, short-term volatility of glacier velocity changes is almost universal.