Calculation of glacier ablation from air temperature, West Greenland

Recent measurements by the Geological Survey of Greenland (GGU) confirm a relation between glacier ablation and air temperature expressed in the form of positive temperature sums. The relation has already been used for the simulation of runoff from glacier-covered basins but might also be suitable for calculating ablation under alternative climates.
The degree-day factor, linking ice ablation to positive temperature sums, shows no distinct seasonal variation although it does fluctuate to some extent from year to year and possibly according to location. There is no evidence that the model can be improved by including incoming shortwave radiation but variations of winter snow accumulation have an important effect on summer ablation. This can be expressed by using a lower degree-day factor for snow than for ice.
Ablation can also be calculated from summer mean temperature although less accurately than using positive temperature sums. For example, ablation will increase substantially if summer temperatures rise due to greenhouse-effect warming of the atmosphere.