Abstract
ABSTRACTKnowledge 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 (Lin), but notable differences in precipitation, incoming shortwave radiation (Sin) and wind speed. Under the prevailing regional precipitation and debris conditions, more Lin (42 W m−2) was supplied from warmer and more humid air and more Sin (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 <~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 Sin and the sensible heat flux.
Highlights
The glaciers in the Himalaya and Tibetan Plateau are the sources of the major rivers of Asia (Immerzeel and others, 2010), and in addition, their status is a sensitive indicator of regional climate change at high altitudes where few meteorological data are available
The air is warmed by radiative and convective heating from the underlying debris during daytime (Brock and others, 2010). These cooling/warming effects contribute to the observed differences in daily and diurnal temperature variations between the debris-free Parlung No 4 Glacier and the debris-covered 24 K Glacier (Figs 5a and 6a)
To investigate the melting magnitudes and their controlling energy fluxes under different extreme weather conditions, the energy fluxes between clear-sky and overcast weather conditions were compared between Parlung No
Summary
The glaciers in the Himalaya and Tibetan Plateau are the sources of the major rivers of Asia (Immerzeel and others, 2010), and in addition, their status is a sensitive indicator of regional climate change at high altitudes where few meteorological data are available. Both debris-free (clean) glaciers and debris-covered glaciers are common in the Himalaya and Tibetan Plateau (Benn and others, 2012). The complex orography results in major climatic variability over short horizontal/vertical distances (Maussion and others, 2013) and the representativeness of limited measurements needs to be addressed
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