Abstract. The Siberian Altai covers about 70% of the area of all south Siberian glaciers, which provide fresh water to the upper tributaries of the Ob and Yenisey rivers. The observed air temperature has increased by 1.2 °C over northern Eurasia during the last 120 years, affecting the degradation of the Siberian Altai glaciers. In this study, we estimated glacier area changes in the Aktru River basin (44.8 km²), located in the central Altai mountains. We used the 1952, 1966, 1975 and 2006 remote sensed images with 0.6–3.0 m spatial resolution (aerial photographs, Corona and PRISM satellite images) and differential GPS (DGPS) data. From 1952 to 2006, the total glacier area in the Aktru basin shrank by 7.2% (1.2 km²). During the last three decades, the rate of glacier area loss increased by a factor of 1.8, thus resembling trends in other mountain systems of Eurasia (Alps, Tien Shan). The glacier area changes were caused mainly by increase of summer air temperature by 1.03 °C (from 1951 to 2000) at elevations below 2500 m, which intensified the melt of the glacier's ice in the ablation zone. At elevations above 2500 m (upper accumulation zone), the summer air temperature increased by only 0.83 °C.

Received 13 June 2007, accepted for publication 1 November 2007
Published 26 November 2007