Estimation Of Glacier Velocity And Analysis Of Spatio-temporal Characteristics Based On Multi-source Remote Sensing In The Three-river Headwaters Region

Glaciers are indicators of climate change and are the largest source of fresh water on Earth.With the warming of the climate,the glacier changes in the Three-River Headwaters Region are increasing,so it is of great significance to monitor the glaciers in the Three-River Headwaters Region.Glacier movement is an inherent attribute of glaciers.The rapid development of remote sensing technology and Sentinel-1 highrevisit period images provide powerful help for glacier movement monitoring.Based on the Sentinel-1 SAR data,Sentinel-2 optical data,ICESat-2 laser altimeter,and other multi-source data,the glacier velocity is estimated by using the SAR offset tracking and optical offset tracking techniques.The average daily velocity of typical glaciers in the Three-River Headwaters Region from 2017 to 2020 was obtained,and the detection accuracy of different methods was compared and analyzed.The temporal and spatial characteristics of typical glacier velocity were analyzed with the laser altimeter data.The main contents and research results are as follows:(1)The accuracy of glacier velocity based on Sentinel-1 SAR data is better than the monitoring results based on Sentinel-2 optical data,with an average daily velocity up to 5 cm/d.(2)There are obvious spatial distribution differences in the daily average flow velocity of Geladandong glacier group,which shows that the west part is larger than the east,and the interannual variation characteristics show a trend of first decreasing and then increasing.(3)The daily average velocity of a typical glacier is significantly affected by the topography,which is characterized by a decrease in altitude and seasonal fluctuations.The velocity reaches its maximum value from July to September,and the velocity value is the smallest from November to February.(4)Combined with ICESat-2 altimeter data,the relationship between glacier flow velocity and elevation changes in typical profiles is analyzed,and it is shown that the glacier flow velocity is significantly affected by the micro-topography,and the glacier velocity in the "V" terrain area with large elevation differences is larger.The results provide a reference for the study of glacier change under the background of climate change and provide theoretical support for the follow-up monitoring and early warning of secondary disasters caused by glacier movements,such as glacial lake outbursts and glacial debris flow.