Post-Little Ice Age Glacier Recession in the North-Chuya Ridge and Dynamics of the Bolshoi Maashei Glacier, Altai

The glacier recession of the North-Chuya ridge, Altai, after the maximum of the Little Ice Age (LIA) is estimated based on remote sensing and in situ studies of the Bolshoi Maashei glacier. The glacier area decreased from 304.9 +/- 23.49 km(2) at the LIA maximum to 140.24 +/- 16.19 km(2) in 2000 and 120.02 +/- 16.19 km(2) in 2021. The average equilibrium-line altitude (ELA) rise after the LIA was 207 m. The reduction of glaciers was caused by the warming trend, most rapid in the 1990s, and by the decrease in precipitation after the mid-1980s. The volume of glaciers decreased from approximately 16.5 km(3) in the LIA maximum to 5.6-5.8 km(3) by 2021. From the LIA maximum to 2022, the Bolshoi Maashei glacier decreased from 17.49 km(2) to 6.25 km(2), and the lower point rose from 2160 m to 2225 m. After the LIA, the glacial snout retreat was about 1 km. The fastest retreat of the glacier terminus was estimated in 2010-2022 as 14.0 m a(-1) on average. The glacier mass balance index was calculated, with the results showing a strong negative trend from the mid-1980s until now. Strong melt rates caused the increase in the area of the Maashei lake, which could lead to the weakening of its dam, and prepared for its failure in 2012. The current climatic tendencies are unfavorable for the glaciers.