Detecting surface subsidence trends in permafrost areas with undulating terrains using GPS interferometric reflectometry

Abstract

Global navigation satellite system interferometric reflectometry (GNSS-IR) technology has been applied to detect surface deformation in permafrost areas. Affected by terrain, previous studies have mainly focused on GNSS sites located in permafrost areas with uniform flat surfaces; however, the number of sites is small, which limits the expansion of regional research. This study provides ideas for the detection of surface subsidence trends in permafrost areas with undulating terrains using global positioning system (GPS) interferometric reflectometry. We selected the GPS site AB33 in Coldfoot, Alaska, and the GPS signal-to-noise ratio (SNR) data during the 2023 snow-free thaw season were processed to obtain continuous surface reflector heights. Outlier detection of reflector heights to extract robust and reliable information and reflector height change trends were analyzed to identify satellite results of detected surface subsidence trends. Thereafter, hierarchical clustering was performed by azimuth and reflector height to group the satellite results into similar clusters and average them. Finally, the correlation between the surface subsidence trends detected at different azimuth ranges after clustering and the subsidence trends simulated by the thawing index was analyzed. The results showed that the detected surface subsidence trends strongly correlated with the simulated trends, with a maximum correlation coefficient (R) of 0.74. This verifies that the ideas presented in this study can effectively detect surface subsidence trends in permafrost areas with undulating terrains.