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In this paper, we aim to determine the interactions of debris-covered glacier elevation change with some glacial properties (including ice thickness, surface temperature, debris albedo, and supraglacial lakes) over the largest and the most dynamic glacier in Iran, Alamkouh Glacier, using the repeated acquisition of high-resolution remote sensing data and in-situ measurements during 2010–2018. First, we present the elevation change of Alamkouh glacier using digital elevation models (DEMs) derived from unmanned aerial vehicle (UAV) and LiDAR. Results revealed that on the whole glacier area, the LiDAR and UAV datasets achieved a highly consistent estimate of glacier elevation change at − 1.6 ± 0.2 m during 2010 and 2018. On the local scale, datasets revealed a clear constant between moderate elevation change of the two smaller flow units of the glacier (about − 0.48 ± 0.06 and − 0.37 ± 0.04 m) and significantly more negative elevation change in the main flow unit (− 2.5 ± 0.31 m). Results show that the elevation change of the Alamkouh glacier is jointly influenced by supraglacial lakes and the types of glacier cover. The regions where the rates of thinning are greatest coincide with the regions where the supraglacial lakes exist. In contrast, a weak relationship existed between the elevation change and glacier surface albedo and especially ice thickness. We observed a remarkable negative elevation change (− 6.3 m) of areas connected with supraglacial lakes in comparison with clean ice (− 3.1 m) and debris-covered (− 1.71 m) areas. It is proven that the quantity and area of the supraglacial lakes are the key to understanding the melting rate of the debris-covered glacier. Our observations infer the significant insulating function of debris cover on the Alamkouh glacier and highlight the effect of supraglacial lakes on enhancing glacier wastage. [ABSTRACT FROM AUTHOR]

Snout monitoring of the Gangotri glacier (Uttarakhand, India) during the ablation season (May to September) in years 2005 and 2015 by using rapid static and kinematic GPS survey reveals that the retreating rate has been comparatively more declined than shown by the earlier studies. Our study is based on the individual measurement by the remote sensing, added by the ground observations by using Differential global positioning system (DGPS) to determine the precise recession rate of the glacier at sub-centimeter level of accuracy. The GPS dataset show that the total average retreat along the snout has been 102.57 ± 0.05 m from 2005 to 2015 with an average rate as 10.26 ± 0.05 m/yr. Additionally, the shift in snout position was also measured through multi-temporal satellite data from 1989 to 2016. The results indicate that the Gangotri glacier snout has retreated by 585.62 ± 38.30 m during this period with an average retreat of 26.75 ± 4.36 m/yr from 1989 to 1999, 21.58 ± 3.77 m/yr from 1999 to 2009 and 14.60 ± 4.81 m/yr from 2009 to 2016. Such a decline in retreat is further confirmed by the satellite data set. A close examination of meltwater discharge and retreating rate (r2 = 0.95) show that both parameters are strongly correlated. Therefore, we suggest that a consistent decrease in meltwater discharge from 1999 to 2015 is in agreement with decreasing trend of retreating rate during the recent years. To determine the possible causes of decreased retreating rate, a relationship between debris thickness and melt rate was also established by ablation stakes. Further, we infer that the declining trend in the glacier retreat is not only controlled by prevailing weather conditions (rainfall and air temperature) but is also governed by increased debris cover on the glacier surface which prevents the ice to melt. [ABSTRACT FROM AUTHOR]