A geometric glacier model for sea-level change calculations

Towards accounting for the dynamic response of glaciers and ice caps in the estimation of their contribution to sea-level rise due to global warming, a mass-balance degree-day model is coupled to a geometric glacier model. Th e ice dynamics are treated implicitly in the geometric model by using scali ng parameters that have been extensively investigated in the literature. Th e model is tested by presenting a case-study of the glacier Hintereisferner , Austrian Alps. The results are compatible with geomorphological data and other modelling studies. An estimate is made of the volume decrease due to initial disequilibrium. An extensive sensitivity study using generalized gl acier shapes and sizes allows a comparison of results with dynamic theory. According to the geometric model, glaciers with a narrowing channel change more with a change in mass balance than glaciers with a widening channel, d ue to their shape and the way in which that shape changes with a changing c limate. Also their response ti:me is longer. As time progresses after a mas s-balance perturbation, the longer response time for continental glaciers c ompared to glaciers with larger mass turnover offsets the effect of their s maller static sensitivity. Thus, although for the next century we may expec t greater changes in volume from alpine glaciers, the equilibrium or commit ted change is greater for the continental glaciers.