Glacier response to the transition from lake- to land-terminating following a glacial lake outburst flood at Jinwu Glacier, southeastern Tibet

Abstract

Proglacial lakes can accelerate terminus retreat and dynamic thinning of lake-terminating glaciers. However, glacier responses to abrupt lake disconnection following glacial lake outburst floods (GLOFs) remain poorly quantified. Here, we investigate the dynamic evolution of Jinwu Glacier in southeastern Tibet, China, whose proglacial lake (Jinwuco) drained during a GLOF on 26 June 2020, shifting the glacier from lake- to land-terminating conditions. Following this loss of lake contact, the downstream glacier tongue showed clear changes in ice flow and frontal morphology. Mean ice-flow velocity within 100–200 m of the terminus decreased from 42.97 ± 4.38 m a −1 during 2017–2020 to 24.09 ± 6.71 m a −1 during 2021–2025, corresponding to a reduction of approximately 44 %. During 2020–2021, the glacier front was characterized by ice-cliff degradation and collapse, together with a slight terminus advance of approximately 23 m. In contrast, the glacier tongue upstream of the icefall showed no pronounced velocity change, with mean velocity in the 650–1600 m section changing from 37.55 ± 9.56 m a −1 during 2017–2020 to 35.24 ± 9.37 m a −1 during 2021–2025. The icefall may limit dynamic coupling between the upstream section and the terminus. These results show that GLOF-induced lake disconnection can substantially alter ice flow and frontal morphology near the glacier terminus. This study provides the first quantitative evidence of glacier dynamic adjustment following a GLOF driven transition from lake- to land-terminating conditions.