Subglacial erosion and englacial sediment transport modelled for North American ice sheets

Abstract

Listen

Translate article

Reconstructions of North American glacial history have either been based on interpretation of the geologic record or on numerical models of continental ice dynamics. Because such models make no explicit reference to the geological products of glaciation, the full potential of a combined approach has not been realized. We present the results of a process-based model of sediment production, entrainment, transport and deposition that represents a first step toward uniting these two lines of investigation. In this model basal-ice processes are dependent on ice sheet geometry, hydrology and dynamics. A three-dimensional thermomechanical ice sheet model yields the ice geometry, flow and thermal conditions that are used by a model of subglacial hydrology; together these drive the basal process model. Comparisons of simulation results with mapped debris distributions of the Hudson Bay Paleozoic carbonates and of the distinctive Dubawnt Group are used to test the validity of the transport model. Dispersion of debris radially out of Hudson Bay is greatly overestimated by the model, and dispersion toward the bay equally underestimated. This is because the modelled ice sheet has a single dome over Hudson Bay at glacial maxima, including Last Glacial Maximum, rather than a saddle separating ice domes over Quebec-Labrador and Keewatin. Estimated rates of glacial erosion for the Cordilleran and Laurentide ice sheets are compared against those predicted by the model. The model underestimates these rates because it underestimates the vigour of the quarrying process.