Thaw slump erosion accelerates fluvial sediment transport after a heatwave on the Taymyr Peninsula, Russia

Abstract. Thaw slumps appear to be expanding across much of the Arctic, yet questions remain about the quantity and fate of sediment eroded from these mass-wasting features, its role in downstream material transport, and how erosion evolves after initial failure. Here, we document the watershed-scale consequences of the largest single-initiation thaw slump event to date, which covers more than 30,000 km² on the Taymyr Peninsula in northern Russia. Using automated satellite methods, we track the rapid failure of more than 1,700 individual thaw slumps and record their ongoing post-failure erosion. We use a combination of Landsat and Sentinel-2 data to show that suspended sediment concentrations (SSC) downstream of slump clusters spiked to 2–5x background levels immediately (1–2 days) after the acceleration of thaw slump failure during the 2020 Siberian heat wave. Elevated suspended sediment transport rates scale with the upstream density of slumps and have persisted as slumps continue to erode; sediment transport during the period 2020–2024 is thus unprecedented in the region during the 40-year Landsat record. Although elevated relative to pre-failure, sediment export to the ocean appears to be significantly less than what is transported by rivers into estuaries, suggesting that estuarine storage may account for much of the eroded lost material, potentially transforming estuarine physical processes and threatening aquatic habitat.