SIMULATION OF MASS-BALANCE VARIATIONS ON RABOTS GLACIÄR, SWEDISH LAPLAND

Determination of degree-day factors for snow and ice allowed for the simulation of mass-balance variations on Rabots Glaciär using a simple degree-day model. The model utilizes observed temperature data and winter balance measurements. Winter balance values are used as a surrogate for precipitation data because the record of the latter is discontinuous and often inaccurate. Available meteorological data is insufficient to define vertical gradients in precipitation and temperature. Therefore, the model was tuned by adjusting these gradients within a range of reasonable values. Preliminary results suggest this simple model cannot accurately simulate the mass balance for a particular year. The model does, however, accurately simulate the cumulative net mass-balance for longer intervals consisting of consecutive years. Modeled cumulative net-balances differ from measured values by less than four percent, which is within estimated uncertainties associated with these values. Further assessment of the model’s accuracy will be carried out by comparing simulations of longer-term cumulative balance with measured changes in glacier volume (mass) during the interval 1959-1998. The model will then be used to create a synthetic record of long-term variations of the glacier’s mass balance.