Abrupt permafrost thaw overwhelms vegetation-driven erosion reduction in sediment export on the Tibetan Plateau

Abstract

Vegetation greening and abrupt permafrost thaw are reshaping sediment dynamics across the Tibetan Plateau, yet their relative effects on sediment delivery remain poorly quantified. Here we show that retrogressive thaw slumps are disproportionately important sediment sources, with erosion rates two to three orders of magnitude above undisturbed landscapes and source-to-channel connectivity generally exceeding 60%. Combining multi-decadal satellite observations, high-resolution topographic differencing and cold-region hydrological modelling, we quantify the competing effects of thaw-slump sediment supply and greening-induced erosion reduction. During 2000–2022, thaw slumps delivered more than four times as much non-ice sediment to channels as was reduced by greening, compensating for declining glacier-derived sediment and contributing to increased downstream suspended sediment export. Across permafrost regions, approximately 1.2‰ thaw-slump coverage represents an upper-bound threshold above which thaw-slump sediment delivery exceeds greening-induced sediment reduction. These results show that spatially limited abrupt thaw can outweigh widespread vegetation recovery in regulating sediment delivery from warming permafrost landscapes. Abrupt permafrost degradation through retrogressive thaw slumps can increase sediment delivery to Tibetan rivers, outweighing the greening-induced reduction in sediment export, suggests a study combining multi-decadal satellite observations, topographic differencing, and hydrological modelling.