Topographic associations with glacier albedo in the southeastern Tibetan Plateau

Glacier surface albedo regulates shortwave radiation absorption and mass balance, yet its long-term and spatial variability remains poorly quantified for maritime glaciers in the southeastern Tibetan Plateau (SETP). Using MODIS Terra and Aqua products, we reconstructed daily albedo for 2003–2024 and examined annual mean, melt-season mean, and melt-season minimum albedo in relation to topography, debris cover, snowfall, and mass balance. All metrics declined significantly ( p < 0.05), with Theil–Sen slopes of −0.0015, −0.0016, and −0.0026 per year, respectively. Declines occurred in all six subregions but varied in magnitude and significance, possibly reflecting regional gradients in monsoon moisture transport and snowfall replenishment. Monthly declines were strongest in August and remained significant in November and December ( p < 0.05). Melt-season duration increased by approximately 6 d per decade ( p < 0.05), mainly through delayed termination, extending glacier darkening into the early-winter snow-recovery period. Albedo increased with elevation by 0.106 km ( p < 0.01), and annual mean albedo was higher in accumulation than ablation zones ( p < 0.01). Debris cover was negatively associated with all metrics ( p < 0.01). Despite greater potential solar radiation, south-facing slopes had higher albedo than north-facing slopes; their greater precipitation and snowfall suggest that fresh-snow replenishment may partly offset radiative forcing. Melt-season albedo was generally positively but weakly associated with annual mass balance, with strong subregional variation. Overall, SETP albedo variability reflects surface darkening and monsoonal snowfall replenishment, highlighting the need to consider both ablation and accumulation when assessing glacier responses to warming.