Changes of the mass balance of the Garabashy Glacier, Mount Elbrus, at the turn of 20th and 21st centuries

Abstract

Long-term series of observations on the glacier of the southern slope of Elbrus manifest the change of two climatic periods in the highlands of the Caucasus. During the first one, relatively cold and snowy period of 1982–1997 with a small positive mass balance, the Garabashi Glacier accumulated a layer of 0.8 m.e. The second period (1998–2017) is characterized by rising summer air temperatures and increasing precipitation in the first decade, and catastrophic melting in 2010–2017. The mass balance of the glacier averaged −0.63 m w.e. yr−1, and in some years it reached −1.00 ÷ −1.50 m w.e. yr−1. In the last ten years, frequency of vast anticyclones covering the southern part of the European part of Russia and the North Caucasus increased. Summer temperatures in the Elbrus region rose to almost the level of the 1950s that was the hottest decade of the XX century. Duration of the summer season on the glaciers increased. Active melting resulted in elevation of the equilibrium line of the Garabashy Glacier by 200 m. In the main part of the glacier alimentation area, i.e. at heights of 3800–4000 m, the large parts of the firn area had disappeared, but open ice of the ablation zone had appeared. The former areas of the "warm" firn zone, where up to 35% of melt water retained within the 20‑meter firn thickness, were replaced by the firn-ice zone, and the ice discharge increased. The glacier alimentation is decreased, and its tongue retreats with increasing velocity. Rocks and entire lava ridges release from ice at different levels of the glacier. The inter-annual variations of the glacier mass balance are controlled by intensity of ablation. In the second period, the correlation coefficient of these values reached 0.97 compared to 0.82 in the first one. In total over 36 years of observations, reduction of the glacier mass during the second period resulted in loss of volume (0.05 km3 or 14%), area (0.51 km2 or 11.4%), and of ice layer (11.4 m).

Volume Changes of Elbrus Glaciers From 1997 to 2017

“…The trends in mass loss acceleration of glaciers since the end of the twentieth century are characteristic of both the Caucasus and many other mountain regions of Russia (Khromova et al, 2019). The intensified Elbrus glacier recession reflects the pronounced increase in summer temperatures, especially since 1995, which is accompanied by nearly consistent precipitation rates Rototaeva et al, 2019;Tashilova et al, 2019. The average summer temperature in the high-altitude regions of the Caucasus over the past 30 years has increased by 0.5-0.7 • C (Toropov et al, 2019).…”

“…The thinning rates of Elbrus glaciers tripled more recently (1997-2017) compared to the 1957-1997 period. Our results are in agreement with the long-term mass balance measurements on two benchmark glaciers in the Caucasus. The Djankuat glacier, located 21 km east-south-east of Terskol airfield (Figure S1), has the longest mass balance record extending back to 1968 (Shahgedanova et al, 2007), while the mass balance record for the Garabashi outlet glacier on Elbrus extends back to 1983 (Rototaeva et al, 2019). Glacier-wide and cumulative mass balance records are presented in Figure 7, together with the geodetic estimate.…”

“…(c) Typical radargrams from aerial and ground-based radar measurements. (Figure 1) since 1987 (Rototaeva et al, 2019). Elbrus glacier volume changes were previously estimated by the comparisons between topographic maps based on aerial photographs and topographic surveys produced by the Lomonosov Moscow State University in 1957 and 1997, and on a topographic map completed in 1887 by Podozerskiy (1911), although state-of-theart assessment of the uncertainties of this map has not been done (Zolotarev, 2009).…”

Geochemistry of cryoconite and soils in the Central Caucasus region and its environmental implications

“…As a result, the coverage of glaciers by debris arises till 3%-6% (Stokes et al 2007). During the recent two decades, stable negative mass balance of Garabashi glacier have been observed, about two times lower than normal for the entire observation period (Rototaeva et al 2019). The deposition of dust and black carbon particles is a crucial factor in accelerating the retreat of glaciers (Kaspari et al 2015).…”

Black carbon as a factor in deglaciation in polar and mountain ecosystems: A Review

“…Currently, the reserves of ice and perennial ferns that accumulated in the second half of the 20th century are melting at an unprecedented speed. They are almost exhausted over a considerable area in the zone of 3.700-4.000 m. The cumulative mass balance has reached its minimum value over the past 50 years [78]. Degradation of the glaciation of the Caucasus is noted over the entire observation period by almost all authors [76,79].…”