Recession of glaciers in the Suntar-Khayata Mountains and methodological consideration of its assessment

This study of glacial-cryogenic complexes of Suntar-Khayata Range is a logical continuation of the research started by M.M. Koreysha in 1957–1959. The studied key site is situated in the upstream of the Burgaly River on the northern slope of Mus-Khaya Mountain (2959 m a.s.l.). It includes glaciers № 29–31 and their ice-cored moraines of different ages. Our study is based on field geomorphologic mapping carried out in 2012, as well as on geospatial analysis of multi-temporal high resolution (1–0.6 m) aerial and satellite imagery. The modern terminus elevation of 16 investigated glaciers varies from 2090 to 2350 m a.s.l. It was found that glaciers’ terminal positions have risen on average from 2052±102 to 2226±114 m a.s.l. after 1945 aerial photography. The termini of Glacier № 29 and Glacier № 31 have retreated approximately by 500–650 m, while the ELA has risen by 61±38 m, from 2346±56 to 2407±55 m a.s.l. The total glaciated area has reduced in size by approximately 36%. The surface of Glacier № 31 has lowered by 50–70 m in its terminal part due to ablation. The estimated glacier shrinkage is valid only for the exposed ice area, since the large amount of glacier ice is buried in ablation moraines, glacier-derived rock glaciers and other glacial-cryogenic landforms. Some ice-cored rock glaciers are 30 to 80 m in thickness. A surface ice flow velocity has decreased 5–6 times compared to the 1957–1959 values. A 45-m-deep geothermal borehole drilled in the middle of Glacier № 31 in 1958–1959 has completely melted away and its mouth shifted 150 m down the glacier surface. The drilling equipment of 1958 is now on the top of a steep 70-m-high rock wall which was entirely covered with ice before 1958. This obviously reflects the magnitude of glacier shrinkage.