Influence of Atmospheric Processes on the Dynamics of Kodar Glaciers

Abstract

Based on daily data on the isobaric surface altitude 700 hPa (lower troposphere) of the NCEP/NCAR reanalysis, we carried out an objective classification of synoptic types over the Kodar Range (Transbaikalia) for the period 1970‒2020 and investigated seasonal and interannual variability of cyclonic and anticyclonic weather types frequency. It was found that the advective atmospheric circulation regime dominates at the level of the lower troposphere over the Kodar Range, and cyclonic types prevail over anticyclonic types in all seasons except summer (June‒August). It was further found that the frequency of occurrence of anticyclonic types has had a tendency to increase in summer and decrease in autumn over the last 50 years, and the frequency of cyclonic types has shown a trend to decrease in spring and, conversely, increase in autumn. It is concluded that the atmospheric circulation over the Kodar Range may influence changes in the mass balance of mountain glaciers. According to the ratio of cyclones and anticyclones in different seasons, three main modes of atmospheric circulation were established that govern possible changes in the mass balance of glaciers. Until the mid-1980s, the increased frequency of winter and spring cyclones contributed to stabilization of the glacier mass balance. From the mid-1980s to the early 2000s, the frequency of winter, spring, and summer cyclones decreased and the number of summer anticyclones increased. It is concluded that such conditions contributed to a decrease in winter precipitation and summer cloud cover, an increase in the net radiation and accelerated ablation of glaciers in the 1990s. Since the early 2000s the atmospheric circulation has contributed to a partial restoring of the glacier mass balance.