Basal controls of the grounding line dynamics of buttresses marine ice sheets

The results of numerical studies suggest that the choice of sliding laws affect simulated dynamics of the grounding lines. Sliding laws that depend on the effective pressure imply that basal shear vanishes at the grounding line. Using analytical and numerical approaches we investigate what effects vanishing basal shear play in the dynamics and stability of the buttressed marine ice sheets. Our results show that the steady-state configurations of marine ice sheets with vanishing and non-vanishing basal shear do not differ greatly. In contrast, the time-variant behaviours of such marine ice sheets are drastically different. In response to a stochastic temporal variability in submarine melting, marine ice sheets with vanishing basal shear can exhibit unstoppable retreat while marine ice sheets with non-zero basal shear in the vicinity of the grounding line can exhibit intermittent advance and retreat. These results suggest that basal conditions in the vicinity of the grounding lines exhibit strong control of their dynamic behaviour. They also suggest the importance of the temporal variability of the basal shear in the dynamics of buttressed marine ice sheets.