Reconnaissance study of glacier energy balance in North Greenland, 1993-94

Reconnaissance energy-balance studies were made for the first time at two s ites in North Greenland to compare with conditions in West Greenland. The f ield experiments were planned to save weight because it is expensive to ope rate in North Greenland. The larger energy components (incoming radiation a nd ablation) were measured for 55 days altogether, and the smaller componen ts were evaluated by indirect methods, e.g. turbulent fluxes are calculated from air temperature, humidity and wind speed, to save the weight of instr uments. The energy-balance model is "tuned" by choosing surface roughness a nd albedo to reduce the mean error between measured ablation and modelled d aily melting. The error standard deviation for ablation is only +/-5 kg m(- 2) d(-1), which is much lower than found in West Greenland, due to better i nstruments and modelling in the present study. Net radiation is the main en ergy source for melting in North Greenland but ablation is relatively low b ecause sublimation and conductive-heat fluxes use energy that would otherwi se be available for melting. There is a strong diurnal variation in ablatio n, mainly forced by variations in shortwave radiation and reinforced by noc turnal cooling of the ice surface by outgoing longwave radiation and sublim ation. The model frequently predicts a frozen glacier surface at night el e n when air temperatures are positive.