Mass- and Energy-Balance Modeling and Sublimation Losses on Dokriani Bamak and Chhota Shigri Glaciers in Himalaya Since 1979

Abstract

Available surface energy balance (SEB) studies on the Himalayan glaciers generally investigate the melt-governing energy fluxes at a point-scale. Further, the annual glacier-wide mass balance (Ba) reconstructions have often been performed using temperature-index (T-index) models. In the present study, a mass- and energy-balance model is used to simulate the Ba on Dokriani Bamak Glacier (DBG, central Himalaya) and Chhota Shigri Glacier (CSG, western Himalaya) using the bias-corrected ERA5 data from 1979 to 2020. The model is calibrated using in-situ Ba and validated against available in-situ altitudinal and geodetic mass balances. DBG and CSG show mean Ba of −0.27 ± 0.32 and −0.31 ± 0.38 m w.e. a−1 (meter water equivalent per year), respectively, from 1979 to 2020. Glacier-wide net shortwave radiation dominates the SEB followed by longwave net radiation, latent heat flux, and sensible heat flux. The losses through sublimation are around 22% on DBG and 20% on CSG to the total ablation with a strong spatial and temporal variability. Modeled Ba is highly sensitive to snow albedo —with sensitivities of 0.29 and 0.37 m w.e. a−1 for 10% change in the calibrated value—on DBG and CSG, respectively. The sensitivity of the modeled mean Ba to 1°C change in air temperature and 10% change in precipitation, respectively is higher on DBG (−0.50 m w.e. a−1°C−1, 0.23 m w.e. a−1) than the CSG (−0.30 m w.e. a−1°C−1, 0.13 m w.e. a−1). This study provides insights into the regional variations in mass-wastage governing SEB fluxes at a glacier-wide scale, which is helpful for understanding the glacier–climate interactions in the Himalaya and stresses an inclusion of sublimation scheme in T-index models.