Glacier change over the last century, Caucasus Mountains, Georgia, observed from old topographical maps, Landsat and ASTER satellite imagery

Abstract. Changes in the area and number of glaciers in the Georgian Caucasus Mountains were examined over the last century, by comparing recent Landsat and ASTER images (2014) with older topographical maps (1911, 1960) along with middle and high mountain meteorological stations data. Total glacier area decreased by 8.1 ± 1.8 % (0.2 ± 0.04 % yr⁻¹) or by 49.9 ± 10.6 km² from 613.6 ± 9.8 km² to 563.7 ± 11.3 km² during 1911–1960, while the number of glaciers increased from 515 to 786. During 1960–2014, the total ice area decreased by 36.9 ± 2.2 % (0.7 ± 0.04 % yr⁻¹) or by 207.9 ± 9.8 km² from 563.7 ± 11.3 km² to 355.8 ± 8.3 km², while glacier numbers decreased from 786 to 637. In total, the area of Georgia glaciers reduced by 42.0 ± 2.0 % (0.4 ± 0.02 % yr⁻¹) between 1911 and 2014. The eastern Caucasus section had the highest retreat rate of 67.3 ± 2.0 % (0.7 ± 0.02 % yr⁻¹) over this period, while the central part of Georgian Caucasus had the lowest, 34.6 ± 1.8 % (0.3 ± 0.01 % yr⁻¹), with the western Caucasus intermediate at 42.8 ± 2.7 % (0.4 ± 0.03 % yr⁻¹).