Surface displacement induced by seasonal ground thaw, measured by synthetic aperture radar in the Daisetsu Mountains, Japan

Abstract

Permafrost, which is widely distributed in cold regions, has been greatly affected by recent climate change. Thawing of permafrost, especially in mountainous areas, can change the stability of the ground. Clarifying the dynamics of mountain permafrost is important for constructing climate change adaptation measures, and so is the development of monitoring methods for these measures. In this study, field observation and Interferometric Synthetic Aperture Radar (InSAR) analyses were conducted to detect seasonal thaw subsidence in the Daisetsu Mountains, Hokkaido, considered to have the widest mountainous permafrost in Japan. A field observation carried out during the snow-free season in 2020 resulted in more than 2 cm seasonal subsidence from the end of May through June, followed by more than 0.5 cm in subsidence through the end of August. InSAR results have shown that spatial variation in subsidence coincided with that of wind-swept terrains with almost no vegetation and have the same tendency for change as the field observation data, confirming the effectiveness of InSAR. However, the magnitude of seasonal thaw subsidence in May—June by InSAR was less than 1 cm, smaller than the field observation. This difference is considered result from the difference in spatial representativeness between the leveling survey and InSAR.