A dynamic, vertically integrated, three-dimensional, mass continuity, computer model of the Greenland ice sheet is used to predict the ice sheet's response to climatic perturbation. The ice flow is gravity driven according to glaciological physics, whereby ice flow is claculated as the sum of deformation and sliding components averaged over the ice thickness where longitudinal stresses are considered negligible. The model has inputs of the present-day ice surface and basal topography, and is forced by changes in sea level and surface mass balance, which are modelled by separately described and forced accumulation and ablation parts. The mass balance and the forcing terms are parametized against present-day values and the present-day ice sheet is initially used as the starting condition for model experiments. By repeating model experiments from the same starting point and varying only one model parameter at a time the model's sensitivity to individual parameters is assessed. Characteristic behaviour patterns, reaction times and significant parameters are identified. The model is seen to produce a realistic simulation of present-day conditions. The ice dynamics model is robust compared to the changes that can be introduced by small variations in sea-level. The relationship between forcing temperatures and ablation rates exerts most control on the model. Confidence in the model allows a series of predictive runs to be undertaken to smiulate three types of glacial fluctuation: Short term change, behaviour under maximum ice conditions and deglaciation trends. Whilst climatic forcing is important in driving the model overall, topographic effects and the influences of calving are crucial to understanding maximum state conditions and retreat behaviour. In each of the three cases, the model results corroborate well with what is known about the real world. These matches and the closeness with which the present-day conditions are simulated are mutually supportive to the conclusion that the model is effective and realistic in the way long term ice sheet change in Greenland is represented. The theoretical processes and the model results are considered to describe real processes and events. Modelling, in conjunction with field techniques, is seen as an powerful means of understanding nature.