Glacier surging in the Karakoram continues unabated

The Karakoram mountain range is well-known for its numerous surge-type glaciers of which several have recently surged or are currently surging. Analysis of historic satellite images, topographic maps and reports revealed repeat surges for many of the glaciers, partly back to the 19^th century. The observed surges display a great variety of characteristics regarding surge durations, repeat cycles, flow velocities, advance rates and mass transfer patterns. However, surge mechanisms remain speculative, as the thermal and basal conditions of the glaciers are largely unknown.

Along with positive glacier mass balances and decreasing summer temperatures, the enhanced surge activity in this region is one part of the so-called Karakoram Anomaly. It has been speculated that the Karakoram Anomaly might come to an end, as its mass balance part is showing increasingly negative values, i.e. more similar to the glaciers in surrounding mountain ranges. However, dense time-series of freely available satellite images reveal that this is so far not reflected in a diminishing surge activity, which instead continues unabated.

For this study, animations of Sentinel-2 image quicklooks have been used for early detection of upcoming surges and an analysis of surge development over the past ten years in the central Karakoram. While tributary glaciers continued surging according to their surge cycles, also the much larger trunk glaciers (Panmah and Sarpo Laggo) are now surging again and deform or erase the surge marks of previous tributary surges. In 2024/25, at least 15 glaciers were surging in a small region of the Karakoram, two of which were not classified as of surge-type before. Apart from the animations revealing surge front migration and glacier interactions, time series of flow velocities and surface elevations reveal strong differences in surge dynamics among the glaciers. The 10 m resolution of Sentinel-2 is at the edge of providing meaningful velocity data for the 7 smallest glaciers in the sample.