Multi-layer distribution of Black Carbon and inorganic ions in the snowpacks of western Himalayas and snow albedo forcing

The plausible impact of light-absorbing aerosols on snow darkening and subsequent retreating of glaciers is a global climatic concern. In this study, we present the characteristics of multi-layer distribution and effects of Black Carbon (BC) and inorganic ions in the snowpacks of Khardung (KG) and Phuche (PG) glaciers (>5 km a.s.l.) in the western Himalayas. We observed significant vertical heterogeneity of BC in the snowpacks of KG (~42–428 ng g−1) and PG (~59 and 299 ng g−1), with higher concentrations in aged snow. Similar to BC, ions in the multi-layer snowpack also depicted prominent vertical heterogeneity with strong crustal influence (as indicated by abundant nssCa2+) in the aged snow layers of KG, which also possess a higher snow-melt rate as compared to PG. Among the other inorganic ions, the vertical profiles of nssSO42− and NO3− indicated elution and refreezing effects. The computation of the effective snow albedo for different snow-darkening and snow-physical processes vindicated the need of considering the multilayer model for the accurate quantification of effects of heterogeneous distributions of light absorbing aerosols (LAA) in the snowpacks. Following this, the multi-layer simulations of snow-albedo in the SNICAR model demonstrated the change in snow albedo by 2.5–9.0% for the amount of LAA observed in our study. This resulted in snow albedo forcing of 49.2 Wm-2 for PG, 30.8 Wm-2 for KG1 and 29.6 Wm-2 for KG2 for the typical snow-physical properties in the study region. Comprehensive data sets comprising physical, morphological and chemical properties of aerosols and snow are imperative to predict aerosol-induced snow darkening and the associated anomalous melting of snow/glacier over the Himalayan region.