Effects of Climatic Perturbations on the Surface-Ablation Regime of the Greenland Ice Sheet, West Greenland

The shift of the equilibrium-line altitude by climatic perturbations of air temperature δ T a , absolute humidity δρ v , cloudiness δ w and annual accumulation 6c in West Greenland (EGIG profile) is analyzed by heat-balance modelling. The perturbations δ T a = +1 K, δρ v = +0.25 g m −3 , δ c = +50 kg m −2 result in a shift of the equilibrium-line altitude of 87.5, 9.8, and −24.3 m, respectively, while perturbations in cloudiness are negligible. The most important influence originates from changing air temperature, as air temperature affects daily heat-flux density of melt and duration of the ablation period. In regimes with negative values of the gradient of annual accumulation, the shift of the equilibrium line is enhanced.