Evolution of mass loss at Alamkouh Glacier in Iran using multi-temporal high-resolution DEMs between 2010 and 2023

Small glaciers situated in high mountainous areas are experiencing notable declines, characterized by unprecedented rates of ice loss in recent years. This study investigates the recent changes in surface elevation and mass loss occurring between 2010 and 2023 within the Alamkouh Glacier over three subperiods, one of the biggest glaciers in Iran and the Middle East. These assessments are derived from a combination of high-resolution LiDAR data in 2010 (with a spatial resolution of 20 cm) and multi-temporal surveys conducted using unmanned aerial vehicles (UAVs) in 2018, 2020, and 2023 (with spatial resolutions varied from 10 to 20 cm). The outcomes of this analysis demonstrate that the Alamkouh Glacier experienced an average mass balance of approximately - 0.20 ± 0.04 m w.e.a^-1 from 2010 to 2023. These findings highlight that the Alamkouh Glacier exhibits a relatively moderate rate of mass loss when compared to many other glaciers around the world, as well as to the global average rate of glacier mass loss, which is approximately - 0.5 m w.e.a^-1. The mean mass loss for the specific periods of 2010-2018, 2018-2020, and 2020-2023 was - 0.18 ± 0.03, - 0.24 ± 0.04, and - 0.25 ± 0.04 m w.e.a^-1, respectively. These findings suggest that, although the mass loss of the Alamkouh Glacier remained relatively constant over the entire study period, there was a slight acceleration in mass loss during the latter part of the study. The elevation change analysis reveals extensive heterogeneous patterns of glacier elevation change where the maximum ice loss was observed in areas with supraglacial ponds and exposed ice cliffs, with mean ice thinning rates of approximately - 1.09 ± 0.35 and - 0.73 ± 0.25 m/a, respectively. In contrast, the mean thinning rates for debris-free and debris-covered areas were around - 0.64 ± 0.20 and - 0.20 ± 0.24 m/a, respectively. This variation underscores the significant impact of different supraglacial features on the glacier's overall mass balance, highlighting the complex dynamics of glacier change in response to environmental factors. Our findings underscore the importance of continuous monitoring and detailed modeling to understand the drivers of glacier change and predict future trends, especially using high-resolution UAV data.