Quantifying the effect of a retrogressive thaw slump on soil freeze–thaw erosion in permafrost regions on the Qinghai–Tibet Plateau, China

Abstract

AbstractThermokarst terrain is developing at an accelerating pace in the ice‐rich permafrost on the Qinghai–Tibet Plateau (QTP), China, and the most dramatic of these terrain‐altering thermokarsts is retrogressive thaw slump (RTS). The freeze–thaw erosion (FTE) impacts are sharply increasing on the Plateau due to RTS, especially as a result of the migration of fine sediments in cold climates, these impacts are still not quantified due to the limitation of hydro‐thermal‐mass transport laws in RTS development. Moreover, it is difficult to assess the impact of RTS on the ecology and environment, especially on soil erosion. This study developed a heat–water‐mass transport coupled model of a RTS in the Beiluhe River Region on the QTP, considering the actual topography, water‐ice phase change, latent heat, and surface heat exchange layer. Based on the observed data of ground temperature, unfrozen water content, and heat flux, the coupled model herein is practicable for presenting the geotemperature regime and groundwater flow in the RTS area, thereby quantifying the ice‐rich permafrost thaw and mass wasting. The results presented indicate that: (1) the seepage velocity of the superficial zone (0–1.5 m depth) is two orders of magnitude higher than that of the permafrost table; (2) the mean ice‐rich permafrost thaw volume was 13.4 m2 from 2016 to 2021; and (3) the cumulative mass transport volume was 22 m2 from July 2020 to September 2021. In addition, the relation between the FTE (shown as the migration of sediments) and the amount of ground ice ablation can be fitted by an exponential equation. This work proposes a reliable method for quantifying the effect of FTE and is helpful to assess the eco‐environmental impacts of RTS.