NUMERICAL MODELING OF THE ENERGY-BALANCE AND THE ENGLACIAL TEMPERATURE OF THE GREENLAND ICE-SHEET - CALCULATIONS FOR THE ETH-CAMP LOCATION (WEST GREENLAND, 1155M ASL)

In the present work, a numerical model that calculates the surface energy balance, mass balance and temperature in the uppermost 25 m of ice at a single location on a glacier is presented. The model is forced by five ''basic'' meteorological elements: air temperature and humidity, wind speed, cloud amount and precipitation. The model was developed for studies of the Greenland Ice Sheet. Parameterizations of the surface energy fluxes were optimised with data mainly from the ETH Camp, West Greenland (1155 m a.s.l.). The model was tested on data collected during the summer of 1990 in the ETH Camp. In this case measurements of the radiative fluxes could be used. A reasonable fit between measurements and calculations of mass balance and englacial temperature could be obtained. The energy balance of this summer is discussed. In a second application, the annual cycle of the energy and mass balance and the englacial temperature at the location of the ETH Camp was simulated. In this case long term average values of the input variables were estimated from measurements at other locations and the radiative fluxes were computed with the parameterizations. The effect of model uncertainties on the calculated mass balance and 10 m ice temperature is discussed. The energy balance and the relation between air and ice temperature are analysed. The uncertainty in the calculated ablation is so large (500-1000 mm w.e./yr) that the contribution of ablation on the Greenland Ice Sheet to sea-level rise cannot be calculated with sufficient accuracy (i.e. 60 mm w.e./yr) with this kind of model. However, the model should be appropriate for the determination of the sensitivity of ablation to climate change. It is predicted that at the ETH Camp the mass balance will decrease by 610 mm w.e./yr after a temperature increase of 1-degrees-C.