Quantifying the response of runoff to glacier shrinkage and permafrost degradation in a typical cryospheric basin on the Tibetan Plateau

Glacier shrinkage and permafrost degradation have significantly altered the hydrological processes in cryospheric regions through releasing water and absorbing more energy from the ground. Considering the upper Shule River Basin (USRB) as a typical cryospheric-dominated watershed on the Tibetan Plateau, an extended Budyko framework considering glacier shrinkage and permafrost degradation was constructed to investigate their contributions to runoff change. Runoff exhibited a significant increasing trend during 1970–2015, with a tipping point appearing around 1998. Thus, 1970–1998 and 1999–2015 were identified as the baseline and changing periods, respectively. During the two periods, runoff was the most sensitive to landscape alteration, followed by precipitation. The increase in precipitation contributed 93.1 % to the increase in runoff, while its effect was partially offset by the negative contribution of potential evapotranspiration (−3.9 %). Glacier shrinkage and permafrost degradation accounted for a 8.0 % and 24.8 % increase in runoff, respectively. Part of these increases were offset by changes in other landscape factors (−22.0 %). Our study elucidates the impacts of glacier shrinkage and permafrost degradation on hydrological processes in cryospheric basins.