Caucasus glacier snowcover loss – From a Glaciers Perspective

Ladevali (L), Tsaigmili (T), Baki (B), and Cherinda Glacier (C) in Sentinel false color image from August 30, 2022. Illustrating that each has 10% or less of the glacier surface retaining snowcover.

Several glaciers at the headwaters of the Doira River in the Zemo Svaneti Planned National Park in the Georgian Caucasus have been stripped of snowpack during recent summers. A glacier without a zone a persistent snowcover throughout the year has no accumulation zone and cannot survive (Pelto, 2010). Here we examine Ladevali, Tsaigmili, Baki and Cherinda Glaciers during August of 2016, 2018, 2020 and 2022 using Sentinel imagery. Tielidze and Wheate (2018) completed an inventory of Caucasus glaciers documenting the 1986 glacier surface area at 1482 square kilometers decreasing to 1193 square kilometers by 2014, a 20% decline in this 28 year period. Tielidze et al ( 2022) update this inventory identifying a 23% decline in area from 2000 to 2020, greater than 1% per year.

In 1998 ther Ladvali and Tsaigmili Glacier nearly join at the terminus. Baki Glacier spans the entire upper basin and no lake is evident near Point B. Cherinda Glacier descends a bedrock step to form a lower section. In mid-August of 2018 Baki Glacier has lost nearly all snowcover and a new lake has formed adjancent to Point B. Cherlinda Glacier has a fringe 15% along its upper margin and is no longer connected to lower relict ice below the bedrock step. Ladevali and Tsaigmili Glacier have snow cover above 3200 m covering 15-20% of the glacier and the termini are now separated by ~1 km. At the end of August in 2020 Baki Glacier is snow free. Cherinda has a fringe on its upper maring covering less than 10% of the glacier. Ladevali and Tsaigmili Glacier have snow cover above 3300 m covering ~5% of the glacier. At the end of August 2022 Baki Glacier is again snow free, while Cherinda has a fringe on its upper margin covering 10% of the Glacier. Ladevali and Tsaigmili Glacier have snow cover above 3250 m covering ~10% of the glacier. In 2022 the glaciers also exhibit a lack of retained firn from any recent year, illustrating a consistent lack of retained accumulation. This consistent minimal retained snowcover illustrates that the glaciers cannot survive current climate. A similar situation has been observed further east at Gora Gvandra. The mass balance in the region has continued to decline with a mean annual loss of ~-0.5 m/year from 2000-2019, (Tielidze et al 2022) with 2020-2022 likely even worse

Ladevali (L), Tsaigmili (T), Baki (B), and Cherinda Glacier (C) in Sentinel true color image from August 30, 2020. Illustrating that each has 10% or less of the glacier surface retaining snowcover.

Ladevali (L), Tsaigmili (T), Baki (B), and Cherinda Glacier (C) in Sentinel false color image from August 16, 2018. Illustrating that each has 20% or less of the glacier surface retaining snowcover with several weeks left in the melt season.

Ladevali (L), Tsaigmili (T), Baki (B), and Cherinda Glacier (C) in Landsat image from mid-August 1998. Ladvali and Tsaigmili nearly join in 1998. Baki Glacier expands across the entire basin and Cherlinda descends below a bedrock step.

Khasankoi Glacier in 1985, 1998, 2013 and 2020 Landsat imagery with Point 1-4 indicating locations where bedrock expansion is occurring with Point 1 and 3 separating the glacier into three parts. Note complete lack of snowcover on 8-26-2020.

Khasnakoi Glacier is a north facing slope glacier just south of Mount Elbrus that drains into the Kuban River. The Greater Caucasus contain approximately 2000 glaciers with a total area of ~1200 km2(Tielidze and Wheate, 2018). Significant positive trends in annual and summer temperature from 1960-2014 have driven large overall glacier area loss, 0.53% per year, leading to the loss of over 300 glaciers (Tielidze and Wheate, 2018). Here we examine Landsat images from 1985-2020 to identify key changes of the glacier.

In 1985 the glacier extended 4.6 km from east to west without interruption and featured three primary termini. The glacier in 1985 has an accumulation area ratio (percent snowcovered) of 60%. By 1998 there is limited retreat the glacier is still once continuous glacier and the accumulation area ratio is 40. By 2013 at Point 1 a bedrock ridge is emerging. At Point 2 a few outcrops of rock are evident emerging from under the thinning glacier. The same is the case at Point 4. At Point 5 a new lake has developed at the margin. The accumulation area ratio in 2013 is 25%. In 2020 the accumulation area ratio is 0% snowcover. A pair of ridges now bisect the glacier at Point 1 and Point 3. At Point 2 the rock outcrop has expanded into one large region. At Point 4 a bedrock area has expanded at the head of the glacier. At Point 5 retreat has left the newly formed lake of less than a decade ago isolated from the glacier. This is not the first year of poor snowcover.

The mapped boundary of the glacier below provided by Levan Tieldze illustrates the glacier boundary in 1960, 1986 and 2014, illustrating a 29% decline in area. The loss of snowcover in 2020 is not the first summer when this has been observed in the Caucasus in 2017 Gora Gvandra did not retain snowcover. For Dzhikiugankez Glacier on the slopes of Mount Elbrus there has been a persistent low snowcover by end of summer since 2013. Tieldze (2019) explained the connection of climate to receding glaciers in the Caucasus using Tviberi Glacier in Georgia as an example.

Image from Levan Tieldze indicating the extent of the glacier in 1960 (red), 1986 (black) and 2014 (blue) on a 2016 SPOT image. There is still some connection above Point 1.