Temporary grounding line stabilization on a retrograde bed due to ice plain formation.

Ice plains are large-scale features of the Antarctic Ice Sheet, such as at the front of Institute and Foundation ice streams which feed into the Filchner-Ronne Ice Shelf, but are not reproduced in ice sheet models. In the case of marine ice sheets which are grounded below sea level, the rapid ungrounding of the ice plain, while not directly contributing to sea level rise can affect the flow and ocean-driven melting of the glacier. Thus, it is important that our numerical models are able to produce ice plains when simulating grounding line dynamics. We show the appearance and evolution of an ice plain in a full-Stokes, 2D marine ice sheet model. The ice plains appear where bedrock is over-deepening and as the grounding line stabilises on a retrograde slope. Our modelled ice plains are characterised by a section of lightly grounded ice that is close to hydrostatic equilibrium located upstream of the grounding line, with a break in surface slope further upstream signifying where the basal friction becomes significant. Our modelling shows an ice plain appearing in both retreating and advancing glacier scenarios, and that this behaviour is only present in the model when a basal friction law which accounts for effective pressure at the base is used, rather than a Weertman type friction law with no dependency on effective pressure. This suggests that the choice of basal friction law is especially important when modelling grounding line behaviour of regions where an ice plain is present.