Factors influencing the basal temperatures of a High Arctic polythermal glacier

A number of glaciers in the Canadian High Arctic are composed primarily of cold ice, but the ice at or near their beds reaches the pressure-melting point (PMP) in the ablation zone. Past modelling studies have suggested that the basal temperatures of some of these glaciers reach the PMP where they should not, indicating that they are not in thermal equilibrium with present-day surface air temperatures. To investigate the possible reasons for thermal disequilibria in such glaciers, a two-dimensional ice temperature model was used to simulate the inferred thermal characteristics of John Evans Glacier, Ellesmere Island. Results indicate that while surface refreezing and historical ice-thickness changes have had a warming effect upon basal ice temperatures, supraglacial meltwater reaching the glacier bed provides the single most critical heat source for explaining the apparent thermal disequilibrium between present-day inferred ice-bed temperatures and those modelled under present-day boundary conditions.