The research article ‚Strong acceleration of glacier area loss in the Greater Caucasus over the past two decades‘ presents two new glacier inventories dating from 2000 and 2020 based on optical remote sensing data as well as topographic properties derived from ASTER GDEM dating from 2011. The data contributes to the global GLIMS data base. As the area of investigation is important from the perspective of socioeconomic of even political indications of glacier loss as well as for the long time series which exist there, I consider this study as an important contribution of glacier change assessment.

General comments

The study is clearly structured and presented with a detailed error analysis. What is bit confusing is that the tables and Figures illustrating both inventories are placed in the section ‘5.1 Glacier Inventory 2000‚ and that The histogram of the glacier area distribution displays two lines referring to the elevation distribution within the outlines in 2000 and 2020 which seem to be based on just one DEM. The first issue could be solved by shifting graphs and tables to 5.2, for the histograms I am not sure how realistic this type of area distribution on a fixed altitude is.   

Detailed comments

Line 318: Presenting the Russian Paper of 1911 is a great thing – I would really like to have the inventories a bit better presented. Currently, we only find the number on annual area change rate- but are the older inventories covering the exactly same area and glaciers as the one presented in the study? Could you add total areas?

Figure 11: I would like to have error bars/ uncertainties in this Figure

Figure 12 and captions: I do not get the meaning of the different types of circles – what are nominal glaciers?

Line 377: I think I know what you mean by accumulated loss, but maby cumulated would be clearer?

419: Would be great to have a map or extent of previous inventories replicated if existing and possible due to copyright reasons.

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

By Levan G. Tielidze et al.

Summary

This study presented a new glacier inventory for two time periods (2000, 2020) covering the entire Greater Caucasus (Georgia, Russia, and Azerbaijan) using satellite imagery (Landsat, Sentinel, SPOT) and reported significant area loss in the study area. The manuscript is very well written and nicely structured. I have given some minor suggestions for improvement. The Caucasus region has several debris-covered glaciers and therefore this study mapped these glaciers manually. I could not see results/numbers on debris-covered glacier changes in the manuscript. There is a need to present changes in debris-covered ice in the results section and comparison with other regions in the discussion. Also, in the introduction, there is a need to highlight gap areas in previous glacier inventories and their changes and how the present study is going to fill these gaps.

General comments:

L21: By 2020, glacier surface area had decreased to 1060.9±33.6 km2. After this sentence, you can present results in % which have given at line 24. You can shift this sentence here.

L24, 28, 289, 290-292: -1.16% yr. Present results in single-digit after the point (-1.2% yr). Please carefully check the entire manuscript. At some places, it is single-digit, and at some places in double-digit.

L31: Two glaciers. Please mention here the name of glaciers.

L46: Johansen et al., 2018. Please use any English reference. There is so much published literature on this.   

L52: complete detachment? Glacier or rock? Please correct.

L57-65: I would suggest to highlight gap areas in previous glacier inventories and their change and linking with your study objectives. You have given this gap area at 110 to 127. Please shift these sentences here and modify the text.

L69: GLIMS and RGI ver6?

L154: ‘Topographic details’ such as aspect, slope, and elevation….

L176, 190….: Generally, the glaciology community use the term glacier outline for glacier boundary. Your study used the term contours for glacier boundary at many places and in some places, your study also used outline (L210). Readers may be confused with this term as normally contour represent a line on a map that joins points of equal height or depth. I would suggest to use glacier outline or glacier boundary term instead of glacier contours.

L190: half-pixel buffer size. You can refer here to Bolch et al. 2010. They have given reason for the selection of half-pixel buffer size.

L312: Figure 10. What is the source of the 1960s-1980s data? Please mention this in the caption.

L365, 369: You can show the location of these stations (Terskol and Mestia meteorological stations) in Figure 1.

L367: Negative trend or decreasing trend?

L385: since the 1980s (10 W/m2 over 10 years). How computed this value? or provide a reference here.

L390: Two different pollution events (5/05/2009 and 23/03/2018) are…. provide a reference here.

Reference:

Bolch, T., Menounos, B. and Wheate, R., 2010. Landsat-based inventory of glaciers in western Canada, 1985–2005. Remote sensing of Environment, 114(1), pp.127-137.