Multi-parametric assessment of Nehnar Glacier, western Himalaya: Ice dynamics, debris evolution, geomorphology, and future GLOF risk modelling

Rapid cryospheric changes in the north-western Himalaya are accelerating glacier retreat and increasing the potential for glacial lake outburst floods (GLOFs). This study presents a multi-decadal assessment of the Nehnar Glacier (Jhelum Basin) using satellite data, field observations, ice-thickness modelling, and hydrodynamic simulations. Between 2000 and 2024, the glacier area decreased by 22.2% (1.98–1.54 km 2 ) and the snout retreated by 81 m (3.37 m/a). Mass balance became increasingly negative (−0.82 to −1.21 m w.e./a), resulting in a cumulative ice loss of ∼58.5 Mt (megatons). Ice thickness ranges from 1 to 195 m (mean: 48.35 ± 19.32 m), with an estimated volume of 0.077 km 3 . Geomorphological analysis and modelling indicate the development of a moraine-dammed proglacial lake, currently small (0.007 km 2 ) but projected to expand to ∼0.223 km 2 in an overdeepened basin. Hydrodynamic simulations suggest that a potential future GLOF could generate peak discharges of 17,814–22,700 m 3 /s, inundating up to ∼4.9 km 2 and affecting downstream areas such as Panjtarni and Baltal. While the present lake does not pose an immediate high risk, continued glacier retreat and lake expansion may increase future hazard potential. The findings highlight the need for continuous monitoring and site-specific risk assessment in rapidly evolving glacierized environments of the western Himalaya.