Spatiotemporal Dynamics of Surface Energy Balance over the Debris-Covered Glacier: A Case Study of Lirung Glacier in the Central Himalaya from 2017 to 2019

Debris-covered glaciers, with their intricate thermal dynamics and significant spatial heterogeneity, play a pivotal role in elucidating glacier ablation processes and their responses to climate change. However, existing research on their energy balance predominantly focuses on short-term or localized processes, while the long-term evolution of energy fluxes and the combined effects of debris cover and ice cliffs remain underexplored. This study, focused on the Lirung glacier in the Central Himalaya, leverages multi-source remote sensing data (Landsat 8, MODIS, Planet) in conjunction with meteorological observations and an energy balance model to investigate the spatiotemporal variations in the glacier’s surface energy balance from October 2017 to August 2019. Key findings are as follows: (1) Net radiation flux emerges as the predominant energy driver for ablation, reaching its peak during May–June and substantially outpacing both sensible and latent heat fluxes in magnitude; (2) The energy balance exhibits pronounced spatial heterogeneity, with lower-altitude regions receiving enhanced energy inputs and displaying reduced albedo, thereby magnifying the local ablation flux; (3) The average debris thickness is quantified at 0.55 ± 0.02 m, with thicker debris layers mitigating ablation, while thinner layers exacerbate it; (4) Ice cliffs are characterized by significantly elevated ablation fluxes, with certain areas recording values as high as 1.73 times the glacier-wide mean; (5) The proglacial lake has expanded by 21.1 ± 11.4%, with its temporal variations closely tracking the fluctuations in net radiation flux. These findings provide crucial insights into the energy balance and climate responses of debris-covered glaciers in the Central Himalaya.