InSAR Monitoring Of Surface Deformation Of Permafrost In The Source Area Of The Yellow Rive

The Source Region of the Yellow River(SRYR)is in the permafrost boundary area of the northeastern of Qinghai-Tibet Plateau(QTP),which is very sensitive to climate change.Under the background of climate warming,significant degradation of permafrost has occurred in the Source Region of the Yellow River,including thickening of the active layer and melting of underground ice at the upper limit of permafrost.This will cause periodic freezing and thawing of the surface and long-term subsidence trends.Therefore,ground deformation monitoring is an important method for reflecting permafrost changes.In recent years,Interferometric Synthetic Aperture Radar(InSAR)technology has become a hotspot in the study of permafrost ground deformation due to its advantages of large coverage and spatiotemporal continuity.This study uses 398 SAR data of Sentinel-1 from 2017 to 2021 to obtain ground deformation information in the SAYR based on InSAR technology.The results show that there are significant differences in ground deformation among different sub-basins in the SAYR.The average annual deformation rate of the entire study area is-4.2 mm/a,showing an overall subsidence trend.The average annual deformation rate of the permafrost area is-7.3 mm/a,and the degree of subsidence is significantly higher than the average level of the entire basin.The average seasonal deformation amplitude of the SAYR is 8.85 mm,and the average seasonal deformation amplitude of the permafrost area is 11.2 mm.Subsequently,the differences in ground deformation under different underlying surface conditions in the permafrost area were studied.The results show that there is strong spatial heterogeneity in ground deformation,and surface thermal state,underground ice content,surface vegetation conditions,and terrain will all affect deformation.Among them,terrain is the most important influencing factor on ground deformation,and ground deformation is significantly higher in areas with relatively flat terrain.The annual deformation rate and seasonal deformation amplitude are positively correlated with the annual average low temperature and underground ice content.The annual average ground temperature and terrain elements have a more obvious influence on the annual deformation rate,and there is a higher seasonal deformation amplitude under conditions of extremely good or poor surface vegetation.In addition,under the same underlying surface type,the annual deformation rate and seasonal deformation amplitude of permafrost ground deformation show similar patterns.Finally,the study focuses on analyzing the spatial variations of ground deformation in the sub-basin of the Yellow River with the highest permafrost coverage within the study area.By analyzing existing borehole data and selecting three typical deformation feature points,the study investigates the spatial distribution characteristics of deformation within the sub-basin and the differences in ground deformation of permafrost under the influence of different underlying surface factors.The results show significant spatial distribution differences in ground deformation of permafrost within the sub-basin.The temporal deformation results of borehole points within the permafrost zone show a clear subsidence trend,which gradually weakens from south to north.The areas near the mountains on both sides of the Yellow River and the upstream area of Gyaring Lake show a higher annual deformation rate,exhibiting a clear subsidence trend,while the central river valley exhibits a significant uplift trend.The three typical deformation feature points exhibit different deformation characteristics,with terrain factors being the main factor contributing to the deformation differences between the southern and northern mountains.By monitoring the ground deformation of permafrost in the source region of the Yellow River,this study provides a theoretical basis for the surface subsidence in the permafrost area as well as the degradation of permafrost in this region.Proposing the feasibility of surface deformation as a data support for perennial permafrost distribution maps in perennial permafrost boundary areas,thus providing certain technical support for the research in the field of hydrogeology of the source region of the Yellow River as well as the ecological protection and construction of the project in this region.