Monitoring And Analysis Of Permafrost Deformation In Qinghai-Tibet Plateau Based On Medium-resolution SAR Data

The Qinghai-Tibet Plateau is a typical area with high-altitude permafrost in the middle and low latitudes.With the global climate warming,the permafrost has begun to degenerate,inducing surface subsidence,and further affecting the stability of the plateau's transportation routes and buildings.Large-scale permafrost deformation monitoring is of great significance to the prevention and control of engineering geological disasters,ecological environment protection,and sustainable economic development of plateau residential areas.This paper mainly uses medium-resolution SAR data to monitor the deformation of permafrost in the Qinghai-Tibet Plateau,combined with surface temperature data,to analyze the influence of natural factors and human activities on the changes of permafrost.The specific work is as follows:(1)Using SBAS-InSAR technology to process 103 scenes of Sentinel-1A/B data,the surface deformation sequence from March 15,2015 to December 31,2019 in the Beiluhe permafrost region of the Qinghai-Tibet Plateau was obtained.During the nearly five-year monitoring period,the permafrost exhibited a seasonal change pattern with an annual cycle.The freezing period is from October to March of the next year.The temperature decreases and the frost heave of the active layer rises;the thawing period goes from April to September each year,and as the temperature rises,the active layer melts and sinks.The study area generally shows a sinking trend.The surface deformation rate in most areas is between-10-10mm/y.Obvious deformations are distributed in warm and ice-rich permafrost regions and mountain slopes.The cumulative maximum subsidence reached-141 mm,the cumulative maximum lift reached 73 mm.(2)Using the mono-window algorithm to process 61 scenes of Landsat-8 data,we can obtain land surface temperature data from October 24,2014 to December 25,2019.The surface temperature of the study area has a gradual decrease from the southeast to the northwest,with obvious seasonal changes as a whole and the ground temperature rising in spring and summer,and falling in autumn and winter.The low temperature period is from December to February of the following year.Seasonal lakes and ponds are frozen and part of the ground is covered with snow.The high temperature period is from June to August each year.As the lake and pond thawed,ice layer melted and disappeared,and the snow cover decreased,the surface temperature of the basin area showed a high value.(3)The correlation analysis between frozen soil deformation and temperature shows that the correlation coefficient in the study area varies between-0.82 and 0.8.Most of the regional correlation coefficients are negative,and the correlation coefficients are mainly concentrated around-0.5,showing a moderate negative correlation.Due to the influence of natural factors and human activities in some areas,the negative correlation between deformation and temperature will be changed,showing a positive correlation.Under different natural conditions,the surface temperature has obvious heterogeneity,which further affects the development of permafrost.The lower the surface temperature,the thicker the frozen soil develops and the stronger the negative correlation becomes.The Qinghai-Tibet Railway and the Qinghai-Tibet Highway are used as areas with dense human activities,human activities have a greater impact on the surface,and the negative correlation is weak.