Remote Sensing Monitoring Of Glacier Dynamics In The Source Region Of The Yangtze River From 2000 To 2020

The source area of the Yangtze River is located in the hinterland of the Qinghai Tibet Plateau,with high and steep terrain,crisscross glaciers and rivers,contiguous swamps and wetlands,and scattered lakes,known as the Chinese water tower.Under the influence of global warming,a series of problems have appeared in the ecological environment of the source region of the Yangtze River,such as glacier degradation,shrinking permafrost,desertification in some areas,vegetation degradation and so on.This paper mainly studies the dynamic change trend of glacier area and elevation in the source area of the Yangtze River in recent 20 years from the perspective of remote sensing,hoping to provide relevant decision-making basis for environmental protection and ecological governance in the source area of the Yangtze River.The main research contents are as follows(1)Glacier area changeBased on the Landsat satellite remote sensing data and the second glacier catalogue data,the glacier boundary is extracted by using the method of object-oriented classification and visual interpretation,and the glacier area and change in the source area of the Yangtze River are calculated,and the glacier coverage in different periods is compared.Firstly,according to the distribution of large-scale glaciers in the second glacial catalogue,the study area is divided into three regions: Tanggula Mountain,Kunlun Mountain and redifeng mountain.The glacier areas in different regions are compared to visually show the movement and change direction of glaciers.Then,combined with the glacier elevation data,the glacier changes at different altitudes and slope directions are analyzed.The results show that: the distribution of glaciers in the study area is mainly concentrated in the altitude of 4500-6000 m,and the higher the altitude,the slower the glacier retreat,and the fluctuation of glacier retreat below 5500 m is strong;the retreat rate of glacier area in the northwest slope is the largest,while that in the Southwest slope is the smallest.(2)Glacier elevation changeBased on srtm-dem,alos and aster-gdem data,the glacier elevation change is studied.The glacier boundary vector data obtained in the previous step is mainly used to extract the glacier regional elevation.Firstly,the elevation changes of the whole study area and three glacier regions are analyzed,and then the elevation changes of different elevation regions are studied.The results show that: the overall glacier elevation presents a downward trend,but from 2010 to 2015,the glacier elevation of the three glacier regions presents an upward trend;the higher the altitude of the glacier,the more intense the elevation change,while the elevation change of the glacier between 4500 m and 6000 m is not only violent,but also has no obvious regularity.(3)Climate change in the study areaBased on the temperature and precipitation data of five stations,the trend and mutation analysis were carried out to explore the response of glacier change to climate change in the source region of the Yangtze River.The analysis method is Mann Kendall mutation test,through which the changes of temperature and precipitation can be obtained.Then,combined with the temporal and spatial characteristics of glaciers,it is concluded that the sensitivity of glaciers to temperature is higher than that of precipitation.