Surge-Type Glaciers

Abstract

The Karakoram is one of a relatively few mountain regions with high numbers of surge-type glaciers, subject to sudden, short-lived accelerations that transfer large volumes of ice down glacier. Some 55 surges have been identified since the 1860s involving 46 glaciers. Various studies suggest many more are surge type, perhaps one-third of Karakoram valley glaciers. Existing observations are reviewed and how they compare with those in other, better-known regions. The glaciers involved are predominantly or wholly avalanche-fed; occur in the highest, steepest parts of the Karakoram; and have large elevation spans. In recent decades, many surge-type tributaries have also been identified; 20 out of 33 events since the 1960s and nearly half (22) of all surges are recognised. In the past, most would have been missed, their numbers underestimated. Surges have impacts out of proportion to their short duration, affecting glacier morphology, surface features, hydrology, erosion and deposition. They are explained by instabilities at the bed of the glacier. Timing and recurrence intervals are peculiar to each case and have little or no relation to climate change or fluctuations in adjacent glaciers. They create huge mass balance anomalies and compromise the use of glacier advances or retreats as climatic signals. They pose a range of hazards for nearby communities.