The interaction between thermokarst lake drainage and ground subsidence accelerates permafrost degradation

Abstract

Since it is not viable to directly evaluate permafrost change based on remote sensing, thermokarst lake drainage (TLD) and ground subsidence serve as indicators for depicting permafrost degradation. Unfortunately, the interaction between these two land surface processes as well as their joint effect remain unclear. In this study, based on a homogenized Landsat-Sentinel archive, TLD was detected in the Lena Basin during 2000–2022 thawing seasons using the modified LandTrendr algorithm. Only 9.7% of thermokarst lakes (TLs) experienced remarkable drainage, TLs larger than 30 hm² were more prone to undergone drainage processes. The drainage proportion among TLs with different extents all exceeded 10% during 2013–2015, suggesting the gradual drainage which lasted for three years or longer was likely to be the dominating type. The subsidence rates (−1.64 ± 0.89 to −1.94 ± 1.41 mm per year) surrounding drained TLs were higher than regional average (−1.40 ± 1.19 to −1.60 ± 1.26 mm per year). As the distance to drained TLs decreased, the proportion of subsidence measurements, rates, and seasonal subsidence magnitude exhibited consistent increasing trends. The subsidence rate was higher in the direction of more intense drainage than that in other directions. The ground subsidence trigger TLD by providing meltwater and reducing structural support, while TLD in turn contributes to ground subsidence by forming drainage channels. More importantly, our findings proved that their interaction further accelerates permafrost degradation, which is critical for more accurately modeling the complex permafrost degradation processes under the warmer and wetter Arctic climate.