Comparison of the meteorology and surface energy fluxes of debris-free and debris-covered glaciers in the southeastern Tibetan Plateau

Knowledge of debris-free and debris-covered glaciers is important for understanding the varying response of glaciers to climate change. Measurements at the debris-free Parlung No. 4 Glacier and the debris-covered 24 K Glacier in the southeastern Tibetan Plateau were carried out to compare the meteorology and surface energy fluxes and to understand the factors controlling the melting process. The meteorological comparisons displayed temporally synchronous fluctuations in air temperature, relative humidity and incoming longwave radiation (L-in), but notable differences in precipitation, incoming shortwave radiation (S-in) and wind speed. Under the prevailing regional precipitation and debris conditions, more L-in (42 W m(-2)) was supplied from warmer and more humid air and more S-in (58 W m(-2)) was absorbed at the 24 K Glacier. The relatively high energy supply led mainly to an increased energy output via turbulent heat fluxes and outgoing longwave radiation, rather than glacier melting beneath the thick debris. The sensitivity experiment showed that melt rates were sensitive to energy supply at debris thicknesses <similar to 10 cm. In contrast, energy supply to the Parlung No. 4 Glacier mainly resulted in snow/ice melting, the magnitude of which was significantly influenced by energy supplied by S-in and the sensible heat flux.