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

Abstract

The glacier coverage in the Caucasus Mountains underwent considerable changes during the last decades. Besides a reduction in glacier area which in some areas is comparable to area changes in the European Alps, also the concentration of supra-glacial debris increased on many glaciers. Only a few glaciers in the Caucasus are monitored on a regular basis, while for most areas no field measurements are available on a continuous basis. In this study the regional differences between the well studied Adyl-su basin on the northern slope of the Caucasus is compared with a similar basin in the South (Zopkhito basin). Special focus is laid on the effect of supra-glacial debris cover on the melt conditions during the ablation season. Systematic differences can be shown for the distribution and temporal increase of the debris cover on the glaciers. While in the Adyl-su basin an extensive debris cover on the glacier tongues is common, only some low lying glacier tongues in the Zopkhito basin show considerable supra-glacial debris. Also the temporal increase in debris cover is decidedly stronger in the North. Field experiments show that the thermal resistance of the debris cover is somewhat higher than in other glacerised regions in the world. A simple ablation model which includes the effect of the debris cover on ice melt indicates considerably stronger melt rates in the northern basin, despite the much more widespread debris distribution. This is due to the different meteorological conditions with more frequent cloud cover and precipitation in the South. Still ablation is strongly influenced in both basins by the occurrence of supra-glacial debris cover, reducing the total amount of melt on the glacier by about 20%. Especially in the lower tongue areas this effect mitigates the area loss of the glaciers considerably

Decision Tree and Texture Analysis for Mapping Debris-Covered Glaciers in the Kangchenjunga Area, Eastern Himalaya

“…The thermal analysis of debris cover has important implications: if the thermal resistivity of the debris can be measured or estimated, surface temperature data from ASTER or other sensors can be used to estimate the debris thickness and subsequently the ice ablation rates, as shown by several studies [18,73,75,76].…”

Global glacier volume projections under high-end climate change scenarios

“…For instance, paraglacial processes during deglaciation lead to enhanced rock falls and debris flows from deglaciating mountain slopes and these deliver rock debris to glacier surfaces.This produces debris-covered glaciers 30 and these are common in many mountain regions, including in Alaska, arid Andes, central Asia and in the Hindu KushHimalaya. Thick debris cover (decimetres to metres) limits ice ablation, (e.g., (Lambrecht et al 2011, Pellicciotti et al 2014, Lardeux et al 2016, Rangecroft et al 2016) and reverses the mass balance gradient, with comparatively higher ablation rates up glacier than at the debris-covered terminus. This significantly influences glacier dynamics (Benn et al 2005), and with The Cryosphere Discuss., https://doi.org /10.5194/tc-2018-35 Manuscript under review for journal The Cryosphere Discussion started: 6 March 2018 c Author(s) 2018.…”

The Greater Caucasus Glacier Inventory (Russia, Georgia and Azerbaijan)

“…Glacier retreat appears to be associated with expansion of supra-glacial debris cover and ice-contact/proglacial lakes, which may increase the likelihood of glacier-related hazards and debris flows (Stokes et al, 2007). Debris cover is more common in the north than in the south (Lambrecht et al, 2011;Tielidze et al, 2017).…”