Reconstruction of Glacier Mass Balance and Sensitivity Tests to Climate Change: A case study of Ålfotbreen and Nigardsbreen
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- Geophysical Institute 
A physically-based one dimensional CROCUS snow model was applied to simulate the surface mass balances of Ålfotbreen (1964-2009) and Nigardsbreen (1962-2009) in southern Norway. The required hourly meteorological input data (9 parameters) are obtained from daily data of meteorological observation from stations surrounding the glaciers combined with NCEP 6 hourly reanalysis data to get the diurnal cycle. The results of simulations show that the model was able to simulate the mass balance of Ålfotbreen Nigardsbreen. The correlation coefficients were 0.99 and 0.97 for cumulative mass balance and 0.89 and 0.76 for net balance compared to the observations, respectively. Mass balances for long-term trends are also investigated. According to the model, precipitation changes dominated the contribution of the mass balances changes from the beginning of simulation (1960s) to 1995 for both glaciers. In the last 15 years (1995-2009), temperature changes was the major contributor of mass balance changes for Ålfotbreen, but precipitation was still the major contributor to the changes in cumulative mass balance for Nigardsbreen. The average mass balance sensitivities to temperature were -0.76m w.e./1K and -0.35m w.e./K and to precipitation were 0.33m w.e./10% and 0.18m w.e./10% for Ålfotbreen and Nigardsbreen, respectively. The results of mass balance sensitivity tests indicate that Ålfotbreen is more sensitive to both temperature and precipitation change than Nigardsbreen. Our results also indicate a nonlinear relation between net mass balance sensitivity and temperature perturbation for both glaciers, but no significant non-linearity were found for different precipitation perturbations.