Study On Remote Sensing Monitoring Of Glacier Changes In The Geladandong Region From 1986 To 2020

Glacier changes are one of the most significant indicators of global climate change,and monitoring these changes can help people understand the impact of global climate change on the natural environment.In recent years,with global warming,glaciers have undergone dramatic changes,and rising temperatures have made glacier melting even more intense.Changes in glacier shape and structure can make glaciers unstable and can even trigger natural disasters such as glacier avalanches,glacial lake outbursts,and glacier surges,posing a serious threat to human life and property downstream from the glaciers.Geladandong is located in the hinterland of the Qinghai-Tibet Plateau,where many of China’s major rivers originate.It is one of China’s important water sources,and the rapid retreat of glaciers could affect water supply,which would have a huge impact on the natural environment and social development of China.Multiple glacier surges have also been observed in the Geladandong region,and their impact on the overall changes in Geladandong glaciers remains to be studied.Therefore,this article attempts to study the relationship between surging glaciers and the overall changes in Geladandong glaciers,in order to gain a comprehensive understanding of glacier changes in the Geladandong region.This article is based on the methods of band ratio,DEM registration and differencing,geodetic surveying,and feature tracking.Landsat series remote sensing data and digital elevation data were used to study the changes of glaciers in the Gredandong region from 1986 to 2020.The study obtained information on the glacier area,surface elevation,mass balance,and surface flow velocity changes in the Geladandong region over the years.Finally,combining with meteorological data,the article explores the impact of climate change on glaciers.The main conclusions are as follows:（1）The information of the Geladandong Glacier from 1986 to 2020 was obtained through the Band Ratio Method.The study found that the number of glaciers in the Gelaldandong region remained unchanged,with a total of 255 glaciers.The glacier area has been continuously shrinking.In 1986,1991,2001,2008,2015,and 2020,the glacier areas in the Geladandong region were 951.97km²,938.44km²,925.68km²,923.44km²,878.03km²,and 861.22km².The area has decreased by 90.75km²,with an average annual reduction of 2.67km².The change of glaciers in the Geladandong area was analyzed from the perspective of glacier size,slope and direction,and it was found that the retreat of large-scale glaciers was higher than that of small-scale glaciers,and the glaciers were mainly distributed in the slope range of 0-20°,and the east-facing glaciers retreated more seriously than the west-facing glaciers.（2）Multi-temporal DEM data were used for co-registration and differencing,which revealed the elevation changes in different periods in the Geladandong region.The mass balance of the glaciers in different periods was calculated using geodetic methods.The results indicated that the surface elevation in the Geladandong region had generally decreased,and the glaciers in the area had been in a negative mass balance state.The overall glacier mass balance in the Geladandong region was-0.21±0.02m w.e.·a^-1 from 1968 to 2000,and-0.24±0.04m w.e.·a^-1 from 2000 to 2017.（3）Thirteen glaciers in the Galdangdong region were confirmed to have surged between 1986 to 2020.By analyzing the duration of glacier surges,it was determined that most surging glaciers in the Geladandong region exhibited characteristics of thermally controlled surging glaciers.However,there were exceptions,and by analyzing the behavior of the Gangjiaquba Glacier before,during,and after surging,it was found to exhibit characteristics of hydrologically controlled surging glaciers.Therefore,the triggering mechanism of surging glaciers in the Geladandong region is likely not singular but determined by a combination of hydrological conditions,thermal conditions,and topographical features.（4）By analyzing the climate data from the Anduo Meteorological Station and the Tuotuo River Meteorological Station,it was found that the annual average temperature and annual average precipitation in the Geladandong region have been increasing from 1980 to 2020.Although the increase in precipitation can contribute to the accumulation of glacier mass,the magnitude of the increase in precipitation is still unable to alleviate the retreat of the glaciers.The continuous rise in temperature is likely the primary climatic factor causing accelerated glacier recession,mass loss,and surface velocity reduction in the Geladandong region.