Abstract
The COupled Snowpack and Ice surface energy and mass balance model in PYthon (COSIPY) was employed to investigate the relationship between the variability and sensitivity of the mass balance record of the Halji glacier, in the Himalayas, north-western Nepal, over a 40 year period since October 1981 to atmospheric drivers. COSIPY was forced with the atmospheric reanalysis dataset ERA5-Land that has been statistically downscaled to the location of an automatic weather station at the Halji glacier. Glacier mass balance simulations with air temperature and precipitation perturbations were executed and teleconnections investigated. For the mass-balance years 1982 to 2019, a mean annual glacier-wide climatic mass balance of −0.48 meters water equivalent per year (m w.e. a−1) with large interannual variability (standard deviation 0.71 m w.e. a−1) was simulated. This variability is dominated by temperature and precipitation patterns. The Halji glacier is mostly sensitive to summer temperature and monsoon-related precipitation perturbations, which is reflected in a strong correlation with albedo. According to the simulations, the climate sensitivity with respect to either positive or negative air temperature and precipitation changes is nonlinear: A mean temperature increase (decrease) of 1 K would result in a change of the glacier-wide climatic mass balance of −1.43 m w.e. a−1 (0.99m w.e. a−1) while a precipitation increase (decrease) of 10% would cause a change of 0.45m w.e. a−1 (−0.59m w.e. a−1). Out of 22 circulation and monsoon indexes, only the Webster and Yang Monsoon index and Polar/Eurasia index provide significant correlations with the glacier-wide climatic mass balance. Based on the strong dependency of the climatic mass balance from summer season conditions, we conclude that the snow–albedo feedback in summer is crucial for the Halji glacier. This finding is also reflected in the correlation of albedo with the Webster and Yang Monsoon index.
Highlights
Since the 1850s, an overall glacier mass loss in High Mountain Asia (HMA), which accelerated in recent decades, has been observed (e.g., [1,2,3,4,5,6])
The present study focuses on the atmospheric sensitivity of the Halji glacier in the transition zone between mainly monsoon influenced glaciers to the east and more westerly influenced glaciers to the west
COSIPY is of medium complexity within the range of available surface energy balance (SEB) and mass balance (MB) models [42]
Summary
Since the 1850s, an overall glacier mass loss in High Mountain Asia (HMA), which accelerated in recent decades, has been observed (e.g., [1,2,3,4,5,6]). We statistically downscale the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis ECMWF Reanalysis fifth generation-Land (ERA5L) [41] to the location of an automatic weather station (AWS) installed in the immediate vicinity of the glacier. This 40 year dataset was used to create distributed climate data input fields to force the COupled Snowpack and Ice surface energy and mass balance model in PYthon (COSIPY) [42] to the Halji glacier. The present study focuses on the atmospheric sensitivity of the Halji glacier in the transition zone between mainly monsoon influenced glaciers to the east and more westerly influenced glaciers to the west.
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