A three-dimensional full Stokes model of the grounding line dynamics: effect of a pinning point beneath the ice shelf
The West Antarctic ice sheet is confined by a large area of ice shelves, fed by inland ice through fast flowing ice streams. The dynamics of the grounding line, i.e. the lineboundary between grounded ice and the downstream ice shelf, has a major influence on the dynamics of the whole ice sheet. However, most of the ice sheet models use simplifications of the flow equations, i.e., they do not include all the stress components, and are known to fail in their mathematical representation of the grounding line dynamics. Here, we present a 3-D full Stokes model of a marine ice sheet, in which the flow problem is coupled with the evolution of the upper and lower free surfaces, and the position of the grounding line determined by solving a contact problem between the shelf/sheet lower surface and the bedrock. Simulations are performed using the open-source finite-element code Elmer/Ice within a parallel environment. The effect of a pinning point, inserted beneath the ice shelf, on the ice dynamics is studied to demonstrate the model’s ability to cope with curved and multiple grounding lines. Starting from a steady state, the sea level is slightly decreased to create a contact point between a seamount and the ice shelf. The model predicts a dramatic decrease of the shelf velocities, leading to an advance of the grounding line until both grounded zones merge together, during which an ice rumple forms above the contact area at the pinning point. Finally, we show that once the contact is created, increasing the sea level to its initial value does not cease the interaction with the pinning point and has no effect on the ice dynamics, indicating a stabilizing effect of pinning points.
Authors: Favier, L., Gagliardini, O., Durand, G., Zwinger, T.