Assessment of Glacier Area Change in the Tekes River Basin, Central Tien Shan, Kazakhstan Between 1976 and 2013 Using Landsat and KH-9 Imagery

Abstract. Changes in glacierized area in the Kazakhstani sector of the Tekes River basin were assessed using Landsat and KH-9 imagery from 2013, 1992 and 1976. Between 1992 and 2013, the combined area of 118 glaciers declined from 121.4 ± 9.2 km² to 105.0 ± 5.5 km². The total area loss was 16.4 ± 5.9 km² or 13.5 ± 7.5 %. The rate of area reduction was 0.78 km² a^-1 or 0.64 % a^-1. This rate is lower than in other regions of northern Tien Shan because of the presence of several large glaciers in the sample. The combined glacier area in 2013 exceeds the combined glacier area reported by the RGI5.0/GAMDAM inventories for 1999–2003 by 24 % because the latter did not include glacierized areas on slopes exceeding 40° and a number of small glaciers. Changes in the recession rates between 1976, 1992 and 2013 were examined using a sub-sample of 28 glaciers which occupied 61% of the total glacierized area in 1992 and 64 % in 2013. These glaciers lost 8.3 ± 5.6 % in the 1976–1992 period, 8.4 ± 5.9 % in the 1992–2013 period and 16.0 ± 5.8 % between 1976 and 2013. The recession rates were 0.52 ± 0.35 % a^-1 in 1976–1992 and 0.40 ± 0.28 % a^-1 in 1992–2013 and although they appear to indicate a slow down in the glacier recession, the change in the retreat rates is within the uncertainty of measurement. The relative reduction in glacier area in the sub-sample is lower than for the basin as a whole because of a larger size of glaciers. Temperature increase was observed in all seasons reaching 0.18 °C per 10 years in summer and 0.39 °C per 10 years in autumn in the 1947–2015 period. Precipitation exhibited strong variability declining between 1952 and 1977 and then increasing until 2000s with a number of dry years in the 2010s. There was no statistically significant difference between the means of annual precipitation in the 1952–1977 and 1977–2015 periods. Combined with the nearly steady recession rates, this suggests that it is an increase in summer, late spring and early autumn temperature that drives glacier retreat.