Superficial moraine expansion on the djankuat glacier snout over the direct glaciological monitoring period

Superficial moraine is an inherent attribute of the lower belts of active alpine glaciers at currently prevalent regressive stage of their evolution. Debris on the snout surface influence drastically ablation and mass balance of a glacier and thereby glacier-derived liquid run-off as well. Superficial moraine at the Djankuat glacier, representative for the Central Caucasus, is both examined in the course of direct fieldwork and mapped by means of remote sensing. Debris thickness was mapped thrice during the direct monitoring period as a result of 3 direct surveys, covering the entire debris-covered area of the snout. The study reveals evident debris expansion on the Djankuat snout: covering only 2 % of the entire glacier area in 1968, its share grew up to 13 % by 2010, resulting thereby in 6.5-fold enlargement during 42 years. Debris layer became thicker by 70 cm in some points near the terminus during 1983-2010 whereas volume of lithogenic matter over the whole glacier experienced 141 % increment. This process changed mass balance values and mutilated its spatial pattern. In general, debris cover renders a screening effect upon melt-rate, and thereby glacier-derived liquid bulk run-off turns out to be reduced annually by ca. 20 % on average.