The influence of subtemperate sliding on the formation of temperate ice in ice stream margins

Abstract:

The Siple Coast ice streams are regions of ice that move significantly faster than surrounding ice. Their fast velocities are facilitated by a water-saturated bed, while the bed of the adjacent regions is frozen. The transition between these two regimes takes place in the ice stream margin, where the fast flow transitions to the slow flow of the surrounding regions, resulting in locally high shear stresses and heat dissipation rates. Previous research has shown that this can lead to the formation of temperate ice in the ice stream margin and to outward migration of this margin. Typically, the transition between the frozen and temperate bed is modelled as a no slip to free slip transition. However, this assumption introduces singular stresses at the transition point and neglects the possibility that high stresses or residual water films on the subtemperate side of the bed can lead to subtemperate sliding, as has been observed in other glaciological settings. In this study, we investigate how subtemperate sliding affects the formation of temperate ice in ice stream margins and the migration of these margins. By analysing the boundary layer structure in the margin, we derive asymptotic solutions for the migration speed and quantify its dependence on properties that are available in continental-scale ice sheet models.