Influence of debris cover on the glacier melting in the Himalaya: Fid-Bau Portal

Influence of debris cover on the glacier melting in the Himalaya

Romshoo, Shakil Ahmad / Nabi, Basharat / Dar, Reyaz Ahmad

Abstract Debris cover either enhances or reduces glacier melting, thereby modulating glacier response to increasing temperatures. Debris cover variation and glacier recession were investigated on five glaciers; Pensilungpa (PG), Drung Drung (DD), Haskira (HK), Kange (KG) and Hagshu (HG), situated in the topographically and climatically similar zone in the Zanskar Himalaya using satellite data between 2000 and 2020. Analyses reveals that the HK, KG, and HG had a debris-covered area of ∼24% in 2020, while PG and DD had a debris cover of <10%. Comparing PG to the other four glaciers, it had the highest shrinkage (5.7 ± 0.3%) and maximum thinning (1.6 ± 0.6 m a⁻¹). Accordingly, detailed measurements of PG's debris cover thickness, temperature and ablation were conducted for eleven days in August 2020. The results indicated a significant variation of temperature and the highest melting was observed near dirty and thin debris-covered ice surface. Thermal conductivity of 0.9 ± 0.1 Wm⁻¹ K⁻¹ and 1.1 ± 0.1 Wm⁻¹ K⁻¹ was observed at 15 cm and 20 cm debris-depth, respectively. The ablation measurements indicated an average cumulative melting of 21.5 cm during eleven days only. Degree-day factor showed a decreasing trend towards debris cover depth with the highest value (4.8 mm w.e.°C⁻¹ d⁻¹) found for the dirty ice near the glacier surface and the lowest value (0.4 mm w.e.°C⁻¹ d⁻¹) found at 30 cm depth. The study highlights the importance of in-situ debris cover, temperature and ablation measurements for better understanding the impact of debris cover on glacier melting.

Highlights • The presence of debris cover substantially influences both the rate of melting and the Degree Day Factor of ice mass beneath it. • The ice under a thin debris layer is melting faster (5.4 cm d⁻¹) than compared to the ice underneath thick debris layer (0.5 cm d⁻¹). • The rate at which temperature changes with depth of debris layer is governed by its physical properties.