Annual evaporation from continental type glaciers

Abstract

Annual evaporation, melting and internal accumulation were computed for Xiao Dongkemadi Glacier in the Tanggla Mountains, using a heat transfer model with meteorological elements measured at 5600 m a.s.l. for a period of over a year (May 14, 1992 to May 13, 1993). Estimated total evaporations in melting and non-melting season are 74±10 mm and 46±14 mm, respectively. These amount considered to occupy approximately 10% of annual ablation of the sate. This ratio for Chongce Ice Cap, West Kunlun Mountains where climate is drier was estimated to comprise more than 30%. Our analysis quantitatively confirms that the ablation reduces under drier conditions in spite of increase in the heat supply to the glacier. On the condition of ice exposure, that are often observed in some continental type glaciers in winter, evaporation increeases by 3-5 times depending on optical properties of the ice. Different meteorological elements influence evaporation for different seasons. The water vapor pressure is dominant in the melting season whereas the short-wave radiation is in the non-melting season. Daily evaporation from glacier is governed by two conditions; one is the heat supply and the other is the one for diffusion. The daily evaporation from Xiao Dongkemadi Glacier peaked twice in a year; one in spring and the other in autumn, at an amount of 1 to 1.5 mm. Glaciers in drier or in higher altitude places would show different annual pattern of the evaporation such as those without the autumn peak or with the later spring peak.