The influence of a supraglacial debris cover on the mass balance and dynamics of the Djankuat Glacier, Caucasus, Russian Federation

We have modelled the influence of a supraglacial debris cover on the behavior of the Djankuat Glacier, a northwest-facing and partly debris-covered temperate valley glacier near the border of the Russian Federation and Georgia, which has been selected as a ‘reference glacier’ for the Caucasus region by the WGMS. A calibrated 1D coupled ice flow-mass balance-supraglacial debris cover model is used to assess the impact of the melt-altering effect of various supraglacial debris profiles on the overall steady state characteristics of the glacier. Additional experiments are also carried out to simulate the behavior of this specific debris-covered glacier in a warming future climate. The main results show that, when compared to its clean-ice version, the debris-covered version of the Djankuat Glacier exhibits longer but thinner ablation zones, accompanied by lower ice flow velocities, lower runoff production, as well as a dampening of the mass balance-elevation profile near the terminus. Experiments for warming climatic conditions primarily point out towards a significant delay of glacier retreat, as the dominant process for ice mass loss encompasses thinning out of the ablation zone. The above-mentioned effects are modelled to be increasingly pronounced with an increasing thickness and extent of the superimposed supraglacial debris cover.