Spatial-Temporal Characteristics Of Changes In Glacier Velocity At The Karakoram In The Past 10 Years

Mountain glacier is an important index of global temperature change and its movement reflects the basic process of temperature change.Glacier velocity is an important parameter for mass balance,dynamic modeling and distributed hydrological modeling.In addition,glacier velocity can also be used to estimate the potential damage associated with glacier movement,so the study of glacier velocity is of great significance.Field observation is the traditional method for reliable measurement of glacier velocity.However,this method is time-consuming and labor-intensive,and the working environment is harsh.Moreover,only a few points of information can be obtained,which limits its large-scale application.Remote sensing satellite has the advantages of wide coverage,high resolution and rich historical information.Currently,remote sensing technology has become the main means of monitoring glacier velocity.In the context of climate warming,mountain glaciers in the world are in a state of retreat with strong glacier ablation.However,the Karakoram region is abnormal.Most glaciers in this region are stable or advancing,the ablation area is thickened,and the glacier material increases or is in a state of near equilibrium.In view of this anomaly,this paper studied the variation of glacier velocity in this region from the perspective of glacier velocity.Landsat series remote sensing images from 2013 to2022 were selected to extract glacier surface velocity in the Karakoram region in recent 10 years by using optical image feature tracking method,and the uncertainty of velocity was evaluated.The temporal and spatial variation characteristics of glacier velocity and its response to climate change were revealed.This paper elucidates the temporal and spatial variation characteristics of the velocity of nonsurge-type glaciers,identifies the surge-type glaciers in the study period,and discusses the surge mechanism.The main research contents and conclusions of this paper are as follows:(1)Estimation of interannual glacier velocity in the Karakoram region in recent 10 years.Based on Landsat-8 and Landsat-9 optical remote sensing data,the interannual glacier velocity in the Karakoram region during 2013-2022 was obtained by using optical image feature tracking method,and the uncertainty assessment was carried out.The results show that the uncertainty of glacier velocity estimation is between 3.51 and 9.06m/yr.According to the variation of glacier velocity in this region,spatially,the flow velocity of most glaciers conforms to the law of glacier movement,and the flow velocity gradually decreases from the upstream to the downstream of the glacier.The flow velocity in the center of the glacier is higher than that at the edge of the glacier.In terms of time,the average velocity of glaciers in the Karakoram region showed an increasing trend from 2013 to 2022,with a change rate of 0.94.(2)Temporal and spatial variations of glacier velocity in the Karakoram region from 2013 to2022.From 2013 to 2022,the average annual velocity of nonsurge-type glaciers in the Karakoram region tended to be stable and showed a slight increasing trend.The average velocity was between85.5 and 92.0m/yr,which was consistent with the variation trend of glaciers in the Karakoram region.The central-line velocity changes of three typical glaciers in this region were analyzed.The average central-line velocity of Biafo glacier decreased,while the average central-line velocity of Baltoro glacier and Siachen glacier increased slightly,which was consistent with the change trend of nonsurge-type glaciers.Using the change of velocity and the change of glacier end to identify the surge-type glaciers,it is found that there are 9 surge-type glaciers in the study period.Using the change of velocity of glaciers with shorter intervals,The active phases and quiescent phases of five surgetype glaciers(North(west)branch glacier of Skamri Glacier,Yazghil Glacier,Khurdopin Glacier,Chogo Lungma Glacier,Braldu Glacier)were determined.Among them,the active phases of Skamri North(west)branch glacier and Skamri Glacier were controlled by thermally controlled.The Khurdopin Glacier is hydrologically controlled(3)Relationship between temporal variation of glacier velocity and climate change in Karakoram region.Based on the results of interannual glacier velocity in recent 10 years,the relationship between glacier change and temperature and precipitation in the whole region was studied by using ERA5 meteorological reanalysis data.The results show that the annual mean temperature and summer mean temperature in the Karakoram region have increased gradually since2000.In addition,since 2000,the annual precipitation in this region also showed an increasing trend,while the winter precipitation showed a significant decreasing trend.The change of glacier velocity in the Karakoram region may be influenced by both atmospheric temperature and annual precipitation.