Strong acceleration of glacier area loss in the Greater Caucasus over the past two decades

Abstract

Abstract. An updated glacier inventory is important for understanding glacier behavior given the accelerating glacier retreat observed around the world. Here, we present data from new glacier inventory at two time periods (2000, 2020) covering the entire Greater Caucasus (Georgia, Russia, and Azerbaijan). Satellite imagery (Landsat, Sentinel, SPOT) was used to conduct a remote-sensing survey of glacier change. The 30 m resolution Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model (ASTER GDEM; 17 November 2011) was used to determine aspect, slope and elevations, for all glaciers. Glacier margins were mapped manually and reveal that in 2000 the mountain range contained 2186 glaciers with a total glacier surface area of 1381.5 ± 58.2 km2. By 2020, glacier surface area had decreased to 1060.9 ± 33.6 km2. Of the 2223 glaciers, fourteen have an area > 10 km2 resulting the 221.9 km2 or 20.9 % of total glacier area in 2020. The Bezingi Glacier with an area of 39.4 ± 0.9 km2 was the largest glacier mapped in 2020 database. Our result represents a 23.2 ± 3.8 % (320.6 ± 45.9 km2) or −1.16 % yr−1 reduction in total glacier surface area over the last twenty years in the Greater Caucasus. Glaciers between 1.0 km2 and 5.0 km2 account for 478.1 km2 or 34.6 % in total area in 2000, while it account for 354.0 km2 or 33.4 % in total area in 2020. The rates of area shrinkage and mean elevation vary between the northern and southern and between the western, central, and eastern Greater Caucasus. Area shrinkage is significantly stronger in the eastern Greater Caucasus (−1.82 % yr−1), where most glaciers are very small. The observed increased summer temperatures and decreased winter precipitation along with increased Saharan dust deposition might be responsible for the predominantly negative mass balances of two glaciers with long-term measurements. Both glacier inventories are available from the Global Land Ice Measurements from Space (GLIMS) database and can be used for future studies.

Analysis of Regional Changes in Geodetic Mass Balance for All Caucasus Glaciers over the Past Two Decades

“…Overall, observed mass loss and thickness lowering of all Caucasus glaciers with increased values since 2010 are in good agreement with recent findings of the latest glacier inventory from this region, resulting in accelerated glacier area loss over the past two decades (1.16% yr −1 ), especially since 2014 (1.85% yr −1 ) [37].…”

“…Change in the mass (M) for all Caucasus glaciers over the last 20 years was calculated based on geodetic mass balance data by [3] and the recently published Caucasus glacier inventory by Tielidze et al (2021) [37] based on two different satellite sources from 2000 (Landsat) and 2020 (Sentinel).…”

“…where dm is the average surface balance (−0.53 m w.e. a −1 ) (meter water equivalent per year, no mentioned in the rest part of this paper) for the entire Caucasus in 2000-2019 by Hugonnet et al (2021) [3]; ∆t is the duration of the observation period (20 years); S1 and S2 are the glacier areas at the beginning (1381.5 km 2 in 2000) and at the end (1069.1 km 2 in 2019/2020) of the observation period, according to Tielidze et al (2021) [37].…”

“…Glacier decrease started from the last advances of the Little Ice Age (LIA) in the northern Greater Caucasus, dated approximatively to the late 1840s [35], though it may have been slightly earlier, in the 1810s, in the southern slopes [36]. The decrease rate was relatively small in centennial scale (~0.4% yr −1 in 1911-2014) [22][23][24], while this has increased since the 1960s (0.5% yr −1 ) [21] and reached its maximum rates over the past two decades (1.16% yr −1 ) [37].…”

“…Fourteen glaciers have an area > 10 km 2 resulting in ~220 km 2 or ~21% of the total glacier area in 2020. The Bezingi Glacier, with an area of ~39 km 2 , was the largest glacier mapped in the 2020 database [37].…”