CLIMATE SENSITIVITY OF GLACIERS IN SOUTHERN NORWAY - APPLICATION OF AN ENERGY-BALANCE MODEL TO NIGARDSBREEN, HELLSTUGUBREEN AND ALFOTBREEN

Three glaciers in southern Norway, with very different mass-balance characteristics, are studied with an energy-balance model of the ice/snow surface. The model simulates the observed mass-balance profiles in a satisfactory way, and can thus be used with some confidence in a study of climate sensitivity. Calculated changes in equilibrium-line altitude for a 1 K temperature increase are 110, 108 and 135 m for Nigardsbreen, Hellstugubreen and Alfotbreen, respectively. The corresponding changes in mass,balance, averaged over the entire glacier area, are -0.88, -0.715 and -1.11 m year-1 (water equivalent). Runs with an ice-flow model for Nigardsbreen, to which calculated mass-balance profiles are imposed, predict that the front will advance by 3 km for a 1 K cooling, and will retreat by as much as 6.5 km for a 1 K warming. The response to a 10% increase in precipitation would be a 2 km advance of the snout, whereas a 4 km retreat is predicted for a 10% decrease. This large sensitivity (as compared to many other glaciers) is to a large extent due to the geometry of Nigardsbreen.