Influence of Sub-Debris Thawing on Ablation and Runoff of the Djankuat Glacier in the Caucasus

Abstract

Superficial moraines grew in size during the entire 32-year-long period of direct monitoring of water and ice balance of the Djankuat Glacier in the Caucasus. The total area of debris cover on the glacier increased from 0.104 km2 (3% of the entire glacier surface) in 1968 to 0.266 km2 (8% of the glacier) in 1996. Such rapid dynamics of moraine formation greatly influences the ablation rate and distorts fields of mass-balance components. Sub-debris thawing can be calculated by means of a model, which describes the role of debris cover for the thermal properties of a glacier. Its meltwater equivalent depends mainly on debris thickness. In 1983 and 1994 the debris cover was repeatedly mapped over the whole glacier portion that was covered with morainic material. Sub-moraine ablation increases (vs. pure ice surface) under the thin, less than ca. 7-8 cm, debris layer, whereas the thicker debris cover reduces the liquid runoff due to its shielding effect. Zones differing due to their hydrological effect are depicted on the glacier map and the degree of debris influence on ablation is estimated quantitatively. As a whole runoff from debris-covered parts of the Djankuat Glacier has diminished due to the dominant shielding effect. Variation of the terminus is also shown to be dependent on the evolution of superficial moraine.

Implementation of a process-based catchment model in a poorly gauged, highly glacierized Himalayan headwater

“…Rana et al (1996) reported an average thickness of debris cover of 0.5-1.0 m for the ablation area of Lirung glacier and Langtang glacier (Fig. 1) and therefore a reduction of melt is assumed (see Popovnin and Rozova, 2002). The additional parameter R debris (<1, -0) in Eq.…”

A comparison of glacier melt on debris-covered glaciers in the northern and southern Caucasus

“…Information about the extent of debris cover is available for six years from in situ mapping between 1968 and 1999 (Popovnin and Rozova, 2002). In order to update this information, a Spot Image from 30 August 2006 (with a spatial resolution of 10 m) was used as a reference image for all remote sensing investigations including the glacier boundary delineation.…”

“…According to our observations in the field, the transition between clean ice and a clearly identifiable debris cover is usually not very large on the sampled glaciers and wrong classifications will be of an order of a few pixels. The results were also compared with debris cover maps which exist for Djankuat glacier (Popovnin and Rozova, 2002) and newer mapping results. used a similar approach and achieved satisfactory results for the Djankuat glacier.…”

“…The debris thickness is then assigned to mapped debris cover according to the corresponding elevation difference from the glacier snout as on the glaciers with measured debris thicknesses. For the glaciers in the Adyl-su basin, the thickness measurements on Djankuat Glacier from 2008 could be complemented by detailed debris mapping on this glacier in earlier years (Popovnin and Rozova, 2002). In the Zopkhito basin, the measurements of 2008 and 2009 have been the only ground truth source.…”

Supraglacial debris cover assessment in the Caucasus Mountains, 1986-2000-2014

“…The Greater Caucasus SDC is an important control for ice ablation, as it is similarly in many other glaciated areas (Lambrecht et al, 2011) 35 and has been identified as a key player in glacier mass balance (Popovnin and Rozova, 2002). In addition, in some cases SDC and proglacial lakes are directly related to glacial hazards.…”