Modern Deglaciation of the Altai Mountains: Effects and Possible Causes

Abstract

The analysis of satellite images revealed by 25% decrease of the Altai mountains’ glaciation area over last 50 years. In 2008–2017, deglaciation rate increased twice. This tendency is in good agreement with an observed increase in the Katun River flow by 9% in 2008–2017 as compared to 1940–1968 (under invariable total precipitation). The analysis of trends of main meteorological parameters based on weather station data and the ERA-Interim reanalysis demonstrated that statistically significant warming in the region occurs only during the warm season and does not exceed 0.5°С/10 years. For this reason, “atmosphere–glaciers” turbulent heat transfer has increased by 4 W/m2 in last two years, that caused an annual melting layer increase by 100 mm water equivalent (w.e.). However, the main reason for the Altai mountains’ deglaciation is an increase of downward solar radiation flux, which amounted to 5 W/m2 per decade and increased the melting layer by 365 mm w.e. per year. A positive trend in net radiation agrees well with a decrease in cloud amount, which is associated with an increase in the moisture divergence flux and geopotential height and with the weakening of zonal winds in the middle troposphere.