Hydroclimatic and cryospheric changes in the eastern Pamir Plateau, Tajikistan: A 30-a remote sensing assessment of Yashilkul Lake

High-altitude glacier-lake systems in the eastern Pamir Plateau, Tajikistan, are highly sensitive elements of Central Asia’s cryosphere and are vital for sustaining regional water resources. The Yashilkul Lake is located within a tectonic depression dammed by an ancient rockslide, forming a large alpine lake. This lake is currently impacted by intensified warming, glacier retreat, and poorly quantified hydrological shift. The primary objective of this study is to assess multi-decadal changes in the Yashilkul and Bulunkul lakes and their surrounding cryosphere between 1994 and 2024. The changes were analyzed using multi-temporal Landsat imagery and unmanned aerial vehicle (UAV) surveys, complemented by in-situ meteorological observations from the Bulunkul meteorological station spanning the period from 1990 to 2024. Glacier and lake boundaries were extracted from Landsat data, primarily by applying the normalized difference water index, supplemented by manual delineation. UAV photogrammetry characterized dam morphology and adjacent ponds, and climate trends were evaluated with the modified Mann-Kendall test. A significant warming trend of 0.096°C/a and pronounced interannual precipitation variability have driven persistent glacier retreat and lake surface area fluctuations. The Yashilkul Lake’s surface area decreased from 36.40 (±1.15) km 2 in 2010 to 31.94 (±0.54) km 2 in 2020 and partially rebounded to 33.99 (±0.60) km 2 in 2024, while the Bulunkul Lake’s surface area remained nearly stable owing to limited glacial influence. Additionally, UAV surveys conducted in 2022 and 2024 revealed main features of the Yashilkul Lake: rockslide-dammed origin, perched ponds along the dam body, and an artificial canal regulating its outflow. Nearby glaciers, particularly Glacier No. 369, exhibited strong frontal retreat and proglacial lake expansion. The proglacial lake expanded nearly fourfold from 0.08 (±0.01) km 2 in 2000 to 0.33 (±0.02) km 2 in 2024, raising concerns about potential glacial lake outburst floods that could impact the Yashilkul Lake and compromise the integrity of its natural dam. The findings highlight accelerating hydrological and cryospheric transformations in the Pamir Plateau, emphasizing the need for sustained monitoring of glacier-lake systems owing to their critical implications for water security, ecological stability, and downstream hazard management.