Linking Permafrost Deformation to Active Layer Freeze-thaw Dynamics in the Qinghai-Tibet Engineering Corridor

Abstract. The Qinghai-Tibet Engineering Corridor (QTEC), traversing hundreds of kilometers of sensitive permafrost, hosts critical lifelines increasingly threatened by climate-induced ground deformation and thermokarst disasters. However, we still lack knowledge about the spatiotemporal characteristics of permafrost states and associated ground deformation at a finer scale. Here we derive ~120-m-resolution surface displacements during 2014–2022 from Sentinel-1 interferometric synthetic aperture radar (InSAR) data processing. We disentangle secular displacement rates from seasonal variations, quantified seasonal amplitudes and timings, and determine displacement directions through complementary ascending and descending observations. Results reveal extensive subsidence throughout the QTEC, exceeding 20 mm/year in areas between Golmud and Nagqu. Seasonal deformation, driven primarily by frost-heave, thaw-settlement cycle of permafrost, can surpass 40–80 mm, with valley floors peaking in spring and hillslopes peaking in autumn due to different hydro-thermal and mechanical responses. Seasonal amplitude of vertical displacements effectively constrains ALT, indicating ALT ≥1 m where seasonal amplitude exceeds 55 mm. With the constraint from in-situ ALT measurements and the assumption of a complete ice melt in the fall, a freeze-thaw density-change model pictures a regional map of ALT at high resolution, where the permafrost to the west of QTEC exhibits a greater ALT compared to the eastern section. Alarming numbers of thermokarst phenomena (18 thaw slumps, 2,812 thaw lakes) within 2 km of critical infrastructure underscore escalating hazards. Our findings emphasize the urgent need for integrated monitoring and adaptive strategies to mitigate intensifying risks from permafrost degradation across the QTEC.