International Journal of Applied Earth Observations and Geoinformation (Dec 2021)
Monitoring surface deformation of permafrost in Wudaoliang Region, Qinghai–Tibet Plateau with ENVISAT ASAR data
Abstract
Permafrost in Qinghai–Tibet Plateau (QTP) has been suffering from global warming in recent years, characterized by the deepening of the permafrost active layer. Seasonal changes in permafrost are usually reflected as ground surface deformation, which can be monitored by multi-temporal interferometric synthetic aperture radar (MT-InSAR) technology. Owing to the extreme environment in the QTP, there are few ground-based deformational observation data available, and records of permafrost monitoring by MT-InSAR with ground validation are limited. Here we present a study of surface deformation monitoring for permafrost with MT-InSAR technology validated by a large number of in-situ observations compared with the previous published results. In this study, a small baseline subset (SBAS) method was used with ENVISAT ASAR data in WuDaoLiang, QTP, to acquire the surface deformation and to analyze the corresponding characteristics. The results were first validated with 24 GNSS leveling observation points along the Qinghai–Tibet Railway, including numeric validation (e.g., statistics and KS test) between the InSAR derived deformation and the time-interpolated GNSS leveling values, and the variation trend of the two deformation sequences during a permafrost deformation period, at each observation point. Considering both the differences in magnitudes and trends, the deformation at 22 out of 24 points detected by InSAR corresponded well to the GNSS observation series over one year, which indicates the reliability of MT-InSAR for permafrost monitoring. After validation, the amplitudes and linear velocity of the InSAR deformation in this region were calculated and analyzed, together with selected points in different types of terrain. Generally, in the deformation map, most pixels show a trend of periodic and seasonal displacement, uplift in winter and subsidence in summer, with amplitudes of 3–10 mm in most regions. The deformation in mountain areas is less than that of flat lands in amplitude, and shows more randomness in periodic characteristics. Meanwhile, some points with obvious settlement have been detected, probably corresponding with permafrost degradation.
