Changes in ice-surface debris, surface elevation and mass through the active phase of selected Karakoram glacier surges

Abstract

Surge-type glaciers switch between phases of rapid and slow flow on timescales of a few years to decades. During the active surge phase, large volumes of ice are transported downglacier, creating distinct geomorphological signatures that reflect these dynamic events but ice and sediment transport remain poorly quantified. The impact of surge events, in comparison to non-surge activity, is also unclear. Here, we describe glacier-surface debris and elevation changes through surges on ten different Karakoram glaciers (Khurdopin, Drenmang, Kunyang, Braldu, Chong Kumdan II, Qiaogeli, Saxinitulu, Shakesiga, Skamri and North Crown). We use these data to characterise the surface geomorphological changes during the surges. We also calculate the mass redistribution during each of the surges and compare this to an estimate of overall glacier mass. Repeat geomorphological mapping shows that surface debris transport through the surges leads to widespread rearrangement of surface features, folding and the concentration of debris near glacier termini, confluences and margins. Ice and debris mass redistribution varies between 0.11 and 0.94 Gt per event and shows moderate correlation with total glacier volume (r2 = 0.57) and glacier length (r2 = 0.40). Mass change as a proportion of total glacier volume ranges from about 0.5 to 5% and is moderately correlated with total glacier volume (r2 = 0.43) but not glacier length (r2 = 0.10). The overall conclusion is that surge events in this region account for only a small proportion of overall mass transport, but have an important role in surface debris transport and redistribution, as well as glacier mass balance.