Exploring Controls on the Flow Dynamics of Devon Ice Cap using a Basal Friction Inversion
Accurately predicting the future dynamic contribution to mass loss from the ice caps of the High Arctic requires an improved understanding of the basal conditions of these ice bodies. An adjoint method numerical inversion is therefore applied to elucidate the basal and englacial conditions of Devon Ice Cap in the Canadian Arctic Archipelago, which exhibits a variety of changes to flow dynamics in recent years. These include the surge of Southeast1 and Southeast2 Glaciers, which is suggested to be thermally-regulated. A cryo-hydraulic warming feedback may contribute to the acceleration during this surge as an additional source of heat or water is required for the base of sliding areas to reach pressure melting point. During the active phase of the surge, freezing rates increase as the basal temperature gradient increases dramatically, leading to enhanced conductive heat loss which is not countered by additional frictional heating as the weakened till provides less resistance to flow. The termination of this surge could therefore result from water withdrawal from the underlying till without the need for changes to geometry. Glaciers defined as pulsing consistently had lower basal shear stresses when velocities were higher, but different pulses produced different changes to the basal conditions, making it difficult to suggest a mechanism for these events. The cause of the unequal periods of faster and slower flow observed on the Croker Bay Glaciers also remains uncertain. However, changes to water storage in the till layer are far smaller than interannual variability in surface meltwater reaching the bed, suggesting this could play some role in modulating till strength, thus flow speeds. The bed of Belcher Glacier provides very little resistance to flow near the terminus, supporting the hypothesis that its acceleration is a result of the thinning and retreat of the terminus reducing resistive stresses.
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