Insights from fieldwork on surge-type glaciers with GLOF potential in Gilgit-Baltistan: preliminary results from UAV surveys, GPR surveys, and meteorological measurements 

Glacial Lake Outburst Floods (GLOFs) are a recurring threat in the Karakorum of Gilgit-Baltistan, Pakistan. Numerous surge-type glaciers in the region periodically advance at time intervals of around 10-25 years and dam up streams to create ice-dammed lakes. These lakes empty in sometimes catastrophic outburst floods one to three times a year for several years once an ice dam has formed. Although the downstream population is aware of the risk, early warning systems are being established by the government, and protection measures are being undertaken, even the most recent outburst floods, e.g. at Shishper Glacier, have caused significant damage to essential infrastructure such as the Karakoram Highway and local settlements.In summer 2024 a team of four members of the GOTHECA project carried out fieldwork missions at 6 surge-type glaciers in the upper Hunza Valley and at two glaciers in Shigar Valley. We collected repeat UAV data on eight glaciers, UAV data of GLOF lake bathymetry for three locations, GPR data on three glaciers, temperature gradient data together with local students, and established a weather station in Shimshal Valley thanks to collaboration with partners from Pakistan. The aim of this data collection is to provide ground-truth for satellite data, to better understand the current state and characteristics of local surge-type glaciers, and to better quantify and model past and future GLOFs in Gilgit-Baltistan.We present preliminary results from repeated UAV surveys and from some of the first GPR surveys on these surge-type glaciers in the upper Hunza Valley, providing insights about volumes of former and potential future ice-dammed lakes, ice dynamics, and thermal properties of glacier tongues. With air temperatures of nearly 30 degrees Celsius measured at the tongue of Yazghil Glacier at 3000 m.a.s.l. at noon in summer, daily melt rates were extremely high at more than 0.15 m/day, but the glacier tongue was advancing at several decimeters per day, indicating a potential onset of a surge. Radargrams for three surge-type glaciers indicate alternating zones of warm and cold ice, suggesting polythermal characteristics of these glacier tongues even when not actively surging.