Permafrost degradation of peatlands in northern Sweden
Abstract. Climate heating is degrading palsa peatlands across the circumpolar permafrost region. Permafrost degradation may lead to ecosystem collapse and potentially strong climate feedbacks, as this ecosystem is an important carbon store and can transition to being a strong methane emitter. Landscape level measurement of permafrost degradation is needed to monitor this impact of warming. Surface subsidence is a useful metric of change and can be monitored using InSAR satellite technology. We combined InSAR data, processed using the ASPIS algorithm to monitor ground motion between 2017 and 2021, with optical and LiDAR data to investigate the rate of subsidence across palsa peatlands in northern Sweden. We show that 55 % of the area of Sweden’s eight largest palsa peatlands is currently subsiding, which can be attributed to these permafrost landforms and their degradation. The most rapid degradation occurring in the largest palsa complexes in the most northern part of the region of study, also corresponding to the areas with the highest % palsa cover within the overall mapped wetland area. Further, higher degradation rates were found in areas where winter precipitation has increased substantially. The roughness index calculated from a LiDAR-derived DEM, used as a proxy for degradation, increases alongside subsidence rates and may be used as a complementary proxy for palsa degradation. We show that combining datasets captured using remote sensing enables regional-scale estimation of ongoing permafrost degradation, an important step to-wards estimating the future impact of climate change on permafrost-dependent ecosystems.
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