Process and mechanisms on the occurrence of massive glacier-rock avalanches in the southeastern Tibetan Plateau under anthropogenic warming

Catastrophic mass flows originating from the mountain cryosphere can cause widespread loss of life, destruction of property, and significant geomorphological reworking along flow paths. Based on in-situ field investigations, high-resolution satellite imagery, digital elevation models (DEMs), seismic records, and meteorological data, we present the process reconstruction, triggering mechanism, and downstream implications of a 50 Mm3 ice-rock avalanche and mass flow that originated from 6500 m asl of the Sedongpu basin in southeastern Tibet on 22 March 2021.The avalanche transformed into a highly mobile mass flow which temporarily blocked the Yarlung Tsangpo river. The avalanche flow lasted ~5 minutes and produced substantial geomorphological reworking. This event, and previous ones from the basin (a total of ~50 Mm3 on October 2017 and into 2018 occurring close to the 2021 ice-rock avalanche source region, and the detachment of the low-angle tongue of Sedongpu Glacier in two separate events with a total of ~130 Mm3 on 17/18 October and 29 October 2018), occurred concurrently with, or shortly after periods characterized by record positive air temperature anomalies, which may have contributed to instability of the mountain cryosphere. The occurrence of future large mass flows from the basin under anthropogenic warming cannot be ruled out, and their likelihood and impacts must be carefully considered given potential risks to life and implications for sustainable hydropower and associated socioeconomic development along the Brahmaputra.