Response Of Glacier Variation To Climate Change In The Southern Altai Mountains,During The Last40Years

Mountain glacier is sensitive indicator to climate change, which makes the research of mountain glacier change become a hot topic in the background of global warming. As the second largest water source area in Xinjiang Province, glacier changes have an important practical significance to the ecosystem maintenance of the downstream. We interpret the glacier regions from Landsat MSS/TM of1972a,1989a,2000a and2011a. Glaciers properties were updated refer to World Glacier Inventory and we firstly completed part of glacier inventory in Mongolia. We summarize the structural characteristics of the glacier system and analyze the variation of glacier, temperature and precipitation in the last40years. Different times’ glaciers information was compared, combining with the temperature and precipitation data. The results are as following.First, the glacier regions are interpreted from Landsat MSS image of1972a, and are divided into different glaciers type according to the ridgeline and watershed distribution. Based on those we refresh the glacier properties and supplement part of glacier inventory in Mongolia. The structural characteristics of the glacier system are summarized in Southern Altai Mountains. The results showed that there are about1349glaciers in the study area, with633.91km2in area and66.82km3in reserve. There is opposite change trends of glacier number and glacier area, glacier reserve with the area scale change. The glaciers’distribution shows an obviously asymmetry, glaciers of north aspect are more than south aspect, east aspect are more than the westerns, however the scale of glaciers in south and west aspect are bigger than those in north and east aspect. The glacier scale in Russia is the biggest, followed with China and Mongolia. The glacier number and scale in Kazakhstan are the smallest.Second, the glaciers variation is analyzed from1972a to2011a based on remote sensing of different periods. The results are as following:(1) From1972a to2011a, the glaciers’ area and reserves of the study area respectivcly reduced304.88km2and35.05km3or percentages of the total are48.1percent and52.46percent. The glacial recession rate is1.59percent per year,1.22percent per year and1.23percent per year respectively for1972a to1989a,1989a to2000a and2000a to2011a.(2) The changes of different glacier attributes are not all the same. From different area scales, the smaller glaciers are more sensitive to the climate change. From different aspects, glaciers of south aspect retreat fastest (1.59percent per year); glaciers of south-east’s and north-west’s aspect recession rate are smallest, about0.9percent per year. From different country, the glacier in Mongolia and Kazakhstan shows most significant changes, the glacial recession rate are52.17and68.29percent respectively.(3) The glaciers change in Friendship Peak and Kuytun Peak shows same trend to the whole Southern Altai Mountains. The glacial recession rate is1.12percent per year,0.38percent per year and0.73percent per year respectively for1972a to1989a,1989a to2000a and2000a to2011a.Third, contrast the glacier changes in Southern Altai Mountains to the typical mountain glaciers surrounding our country. The result shows that the glacier change rate in our study area (1.2%·a-1) is bigger than that in the Siberian Altai (0.52%·a-1). From all the statistical results the paper has got, Altai Mountains’glacial recession is bigger compared to the other mountain glaciers in China. The glaciers in the hinterland of Qinghai-Tibet Plateau change is slowest, from where to the north and south glaciers change speed up. These spatial differences of the glacier change are mainly affected by the location, atmospheric circulation and different glacier properties.Fourth, the climate change characteristics are analyzed based on the meteorological grid data. The temperature increased significantly from1972a to2008a, the mean annual temperature has increased1.48℃, about0.40℃·10a-1average temperature in summer and winter has increased0.40℃·10a-1and0.50℃·10a-1respectively. The annual precipitation has increased37.68mm from1972a to2008a, about10.18mm·10a-1. The temperature and precipitation are both showed a certain degree of volatility in the late1980s. Extreme fow temperature appeared from1984to1985, while the precipitation showed a notable increase before1987a, after which showed a fluctuation in little change.Fifth, we compare the characteristics of different times’ glaciers change and climate change, following conclusions are got:(1) There is a good response relationship between the glacier changes and the summer average temperature change. The decreasing of glacial recession rate between1989to2000a(1.59%·a-1to 1.22%·a-1) is responded to the reduction of the summer average temperature from1972to1989a. Then the summer average temperature continued increasing between1989a to2000a after the extreme low temperature in the late1980s, which resulted an increasing of glacial recession rate between2000to2011a(1.22%·a-1to1.23%·a-1). There are about10year’s response lag between the climate change and glacier change.(2) It showed a good positive correlation between the cold season precipitation change and glacier area changes. From1989a to2000a the cold season precipitation showed a significant increase, which corresponded to a decline of glacier retreat rate in the same period. From2000a to2011a the cold season precipitation showed a downward trend, and the glacier retreat rate increased correspondingly. Temperature change plays a dominant role on glacier change. Increase or decrease in precipitation is not enough to affect the overall trend of glacier change.