Ice rises and ice rumples are locally grounded features found in coastal Antarctica and are surrounded by otherwise freely floating ice shelves. In both cases, local highs in the bathymetry are in contact with the ice shelf from below, thereby regulating the large-scale ice flow, with implications for the upstream continental grounding line position. We investigate ice rises and ice rumples using a three-dimensional full Stokes ice flow model under idealised scenarios. The simulations span end-member basal friction scenarios of almost stagnant and fully sliding ice at the ice–bed interface. We analyse the interaction with the surrounding ice shelf by comparing the deviations between the non-local full Stokes surface velocities and the local shallow ice approximation (SIA). Deviations are generally high at the ice divides and small on the lee sides. On the stoss side, where ice rise and ice shelf have opposing flow directions, deviations can be significant. During sea level increase and decrease experiments, transitions from ice rise to ice rumple occur (and vice versa) and divide migration is more abrupt the higher the basal friction. We identify a hysteretic response of ice rises and ice rumples to changes in sea level, with grounded area being larger in a sea-level-increase scenario than in a sea-level-decrease scenario. This hysteresis shows not only irreversibility following an equal increase and subsequent decrease in sea level but also that the perturbation history is important in determining the current ice rise or ice rumple geometry.

Read more: Henry A. C. J., R. Drews, C. Schannwell and V. Višnjević, 2022. Hysteretic evolution of ice rises and ice rumples in response to variations in sea level, The Cryosphere, 16, 3889–3905, doi:10.5194/tc-16-3889-2022