Characterizing the surge behaviour and associated ice-dammed lake evolutionof the Kyagar Glacier in the Karakoram

Glacier surges are prevalent in the Karakoram andoccasionally threaten local residents by inundating land and initiating massmovement events. The Kyagar Glacier is well known for its surge history, andin particular its frequent blocking of the downstream valley, leading to aseries of high-magnitude glacial lake outburst floods (GLOFs). Although the surgedynamics of the Kyagar Glacier have been broadly described in theliterature, there remains an extensive archive of remote sensingobservations that have great potential for revealing specific surgecharacteristics and their relationship with historic lake outburst floods.In this study, we propose a new perspective on quantifying the surgingprocess using successive digital elevation models (DEMs), which could beapplied to other sites where glacier surges are known to occur. AdvancedSpaceborne Thermal Emission and Reflection Radiometer DEMs, High MountainAsia 8-meter DEMs, and the Shuttle Radar Topography Mission DEM were used tocharacterize surface elevation changes throughout the period from 2000 to2021. We also used Landsat time series imagery to quantify glacier surfacevelocities and associated lake changes over the course of two surge eventsbetween 1989 and 2021. Using these datasets, we reconstruct the surgingprocess of the Kyagar Glacier in unprecedented detail and find a clear signal ofsurface uplift over the lower glacier tongue, along with uniformlyincreasing velocities, associated with the period of surge initiation.Seasonal variations in surface flow are still evident throughout the surgephase, indicating the presence of water at the glacier bed. Surge activity of theKyagar Glacier is strongly related to the development and drainage of theterminal ice-dammed lake, which itself is controlled by the drainage systembeneath the glacier terminus.