A 20-year monitoring of seasonal and long-term surface elevation changes in permafrost areas using GPS interferometric reflectometry

Permafrost areas are affected by the annual freeze–thaw cycle, where water-ice phase changes cause surface uplift or subsidence. Global navigation satellite system interferometric reflectometry (GNSS-IR) can effectively quantify these changes. In this study, we retrieved continuous surface elevation changes induced by the dynamics of the active layer and near-surface permafrost (frozen ground dynamics) using global positioning system (GPS) interferometric reflectometry. The SG27 site in a permafrost area (Utqiaġvik, formerly Barrow) was selected, and GPS signal-to-noise ratio (SNR) observations from the snow-free thaw seasons between 2005 and 2024 were processed. We focused on seasonal and long-term trends in surface elevation changes and proposed a stage-specific analysis of seasonal changes using the timing of active layer thickness (ALT; defined as the seasonally maximum thaw depth) measurements. The results revealed: (1) Seasonal trends: the surface experienced obvious subsidence trends during the pre-ALT measurement period, followed by varying trends during the post-ALT measurement period. (2) Long-term trends: although the surface exhibited an overall uplift trend of 0.26 ± 0.01 cm year−1 from 2005 to 2024, a detailed analysis revealed a subsidence trend from 2005 to 2012 (− 0.83 ± 0.03 cm year−1), an uplift trend from 2012 to 2018 (1.29 ± 0.05 cm year−1), and a return to subsidence from 2018 to 2024 (− 0.55 ± 0.04 cm year−1). This study provides further insights into the active layer thaw subsidence patterns and the dynamics of near-surface permafrost.