Abstract:
This paper used the Landsat MSS/TM/ETM/OLI remote sensing image data, digital elevation model (DEM) data and meteorological data from five different periods in 1972, 1989, 1996, 2006 and 2017 are used as data sources, and obtained the glacial lake information in the central part of South Altai Mountains by the method of automatic computer extraction and manual visual interpretation. This paper counted the area of glacial lakes in this area by GIS spatial analysis method, and analyzes the glacial lakes in different scales in the study area. The paper also analysed the slope, temporal and spatial variation characteristics at different elevations. The results show that: ① In the past 45 years, the area of glacial lakes in the central part of South Altai Mountains showed the trend of "decreasing at first and then increasing". From 1972 to 1996, the area of glacial lakes in the study area decreased from 411.14 km2 to 400.83 km2, a total of 10.31 km2 was reduced. The reduction rate of ice lake was 0.43 km2/a. From 1996 to 2017, the area increased by 15.42 km2; to 0.514 km2/a. ②The distribution of ice lakes in the study area is mainly concentrated in the area where the elevation is lower than 2 200 m and the slope is smaller than 25°.The area of glacial lakes in different altitude range and different slope range shows the trend of "decreasing first and then increasing". ②Combining with the analysis of temperature and precipitation data, we find that the change of glacial lake area in the central part of South Altai Mountains has obvious response to regional climate change. Temperature, precipitation and glacier melt water are the main factors affecting the change of glacial lake area. There is an equilibrium relationship among them, that is, the melting rate of glacier increases with the increase of temperature, which has an impact on the balance of revenue and expenditure of glacial lake. When the recharge amount of glacial lake (that is, the sum of glacier melt water and precipitation) is larger than the evaporation caused by rising temperature, the area of glacial lake will increase, and vice versa. The interdecadal precipitation of the whole Altay region decreased by 19.28mm from 1970 to 1980. The temperature increased by 0.25℃, which also led to the evaporation of glacial lake in the study area from 1972 to 1989, larger than that of recharge water, so the area of glacial lakes shrank during this period. From 1989 to 1996, the precipitation in this area increased by 19.67%, and the temperature increased by 0.62℃, but the increased precipitation cannot make up for the evaporation amount of glacial lake caused by the increase of temperature. Therefore, the area of glacial lakes in the study area from 1989 to 1996 is still in a state of retreat. From 1996 to 2017, the area of glacial lakes showed a growing trend due to the increase of temperature and precipitation.