Permafrost thaw dictates erodible landscapes and fluvial sediment dynamics on the Tibetan Plateau

Suspended sediment flux (SSF) in cold environments is a crucial proxy to link glacial, periglacial, and fluvial systems and highly relevant to hydropower operation and aquatic ecosystems. However, the response of SSF to climatic and cryospheric changes in cold environments remains poorly investigated due to the lack of long-term monitoring and the complexity of sediment cascade. Here we show that the water and sediment dynamics in the permafrost-dominated headwater of the Yangtze River on the Tibetan Plateau is driven by thermally-induced permafrost thaw, on a basis of 33-year daily in-situ observations (1985-2017). Air temperature dominates the seasonal pattern of discharge and SSF by controlling the active erodible landscapes. In contrast, rainstorms dominate the shorter-lasting fluvial extreme events. The SSF has been increasing substantially along with the expanding erodible landscapes over the past decades. In a warmer and wetter future for the Tibetan Plateau, the SSF of similar permafrost rivers will probably continue to increase with expanding erodible landscapes and more extreme weather events. The substantially increased fluvial sediment and its asscociated nutrients, pollutants, and organic carbon, have important implication for downstream cascade reservoirs, water quality, and riverine carbon cycle. We urge that SSF should be measured in more headwater rivers on the Tibetan Plateau, in order to accurately predict how SSF in cold environments responses to ice-snow-permafrost melting in the context of ongoing climate change.