Glacial debris cover and melt water production for glaciers in the Altay, Russia

Abstract. Glaciers are important water storages on a seasonal and long-term time scale. Where high mountains are surrounded by arid lowlands, glacier runoff is an important source of water during the growing season. This situation can be found in the Altay mountains in Southern Siberia, where the recent glacierization of >700 km² is subject to continuous mass loss, even though the shrinking is comparably slow. The glacier retreat is accompanied by an extension of supra-glacial moraine, which itself strongly influences ablation rates.

To quantify these effects, the spatial evolution of debris cover since 1952 was analysed for three glaciers in the North Chuya Ridge using satellite and airborne imagery.

In summer 2007, an ablation experiment was carried out on debris covered parts of Maliy Aktru glacier. Thermistors in different depths within the moraine provided data to calculate thermal resistance of the debris. A set of ablation stakes was installed at locations with differing debris thickness and observed regularly throughout the entire melt season. Air temperature from an AWS was used to calculate degree day factors in dependence of the debris thickness. To take into account the shading effect of surrounding walls and peaks, the potential solar radiation and its evolution throughout the summer was determined from a digital elevation model. This allows us to extrapolate our measurements from Maliy Aktru to the other two glaciers of the Aktru basin and to estimate basin melt rates. In addition accumulated ice melt was derived for 12 glaciers in the North Chuya Range. Changes in summer runoff from the 1960s are compared to the results from our melt model and the evolution of debris cover is analysed in respect to the melt activity.