标题：Multi-decadal geomorphic changes of a low-angle valley glacier in the East Kunlun Mountains: remote sensing observations and detachment hazard assessment
摘要：Detachments of large parts of low-angle mountain glaciers inrecent years have raised great attention due to their threats to lives andproperties downstream. While current studies have mainly focused onpost-event analysis, a few opportunities have presented themselves to assessthe potential hazards of a glacier prone to detachment. Here we present acomprehensive analysis of the dynamics and runout hazard of a low-angle(∼20∘) valley glacier, close to the Qinghai–Tibetrailway and highway, in the East Kunlun Mountains on the Qinghai–TibetPlateau. The changes in morphology, terminus position, and surface elevationof the glacier between 1975 and 2021 were characterized with a stereo-imagepair from the historical KH-9 spy satellite, six digital elevation models(DEMs), and 11 high-resolution images from Planet Labs. The surface flowvelocities of the glacier tongue between 2009 and 2020 were also trackedbased on cross-correlation of Planet images. Our observations show that theglacier snout has been progressively advancing in the past 4 decades,with a stepwise increase in advance velocity from 4.55±0.46ma-1 between 1975 and 2009 to 30.88±2.36ma-1 between 2015 and 2020. DEM differencing confirms theglacial advance, with surface thinning in the source region and thickeningin the tongue. The net volume loss over the glacier tongue was about11.21±2.66×105 m3 during 1975–2018. Imagecross-correlation reveals that the surface flow velocity of the glaciertongue has been increasing in recent years, with the mean velocity below4800 m more than tripling from 6.3±1.8ma-1 during2009–2010 to 22.3±3.2ma-1 during 2019–2020. Witha combined analysis of the geomorphic, climatic, and hydrologic conditionsof the glacier, we suggest that the flow of the glacier tongue is mainlycontrolled by the glacier geometry, while the presence of an ice-dammed lakeand a supraglacial pond implies a hydrological influence as well. Taking thewhole glacier and glacier tongue as two endmember avalanche sources, weassessed the potential runout distances of these two scenarios using theangle of reach and the Voellmy–Salm avalanche model. The assessments showthat the avalanche of the whole glacier would easily travel a distance that would threaten the safety of the railway. In contrast, the detachment of theglacier tongue would threaten the railway only with a small angle of reachor when employing a low-friction parameter in the Voellmy–Salm modeling.
