Rapid and massive 335 million m3 glacier bed erosion after detachment of the Sedongpu Glacier (Tibet)

Abstract

Following the 130 106 m3 detachment of the Sedongpu Glacier (south-eastern Tibet) in 2018, the Sedongpu valley underwent drastic and rapid large-volume landscape changes. Between 2018 and 2022, and in particular during summer 2021, an enormous volume of in total ~335 106 m3 was eroded from the former glacier bed, forming a new canyon of up to 300 m depth, 1 km width and almost 4 km length. The mass was transported into the Yarlung Tsangpo (Brahmaputra) River and further. Several rock-ice avalanches of in total ~150 106 m3 added to the total rock, sediment and ice volume of over 0.6 km3 that were exported from the basin since around 2017. The recent events at Sedongpu Glacier represent a rapid and irreversible process of landscape transformation from a sediment-filled glacier valley to a glacier-free one with a deeply incised canyon, impressively confirming that glaciers are able to protect their soft beds against massive erosion. Once uncovered, the erosion potential of soft glacier beds is here demonstrated to be possibly enormous for some glaciers in terms of volumes and rates. Such erosion could be particularly extreme for fine-grained subglacial sediments and for elevated glacier beds where large amounts of subglacial sediments are stored. The 2018–2022 landscape development at Sedongpu represents an extreme example of rapid paraglacial slope response highlighting extreme glacier erosion potentials and related hazards from debris flows and impacts on rivers. Such consequences of climate change in glacierized mountains have so far not been considered at this magnitude.