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

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Abstract
The shift of the equilibrium-line altitude by climatic perturbations of air temperature δTa, absolute humidity δρv, cloudiness δwand annual accumulation 6c in West Greenland (EGIG profile) is analyzed by heat-balance modelling. The perturbations δTa= +1 K, δρv= +0.25 g m−3, δc= +50 kg m−2result 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.