A mixed-bed subglacial hydrology model applied to the Antarctic Ice Sheet

A significant part of the uncertainty of the future contribution of the Antarctic ice sheet to sea-level rise stems from unknown subglacial conditions such as geology and water content. Sliding at the base of the ice sheet depends on geological conditions, as water routing differs between soft and hard beds regions. However, ice sheet modelling studies usually do not distinguish between these different types of bed properties and instead assume it to be constant across the model domain. Also, current subglacial hydrology models have a high computational cost and their application to ice sheet models is often limited to the initialization stage.A recent subglacial hydrology model by Kazmierczak et al. (2024) overcomes these challenges by introducing simplifications that allow to simultaneously account for hard, soft, and mixed beds, as well as efficient and inefficient drainage. The hydrology model is computationally fast, hence it can be easily fully coupled to any ice sheet model.In this study, we apply this new subglacial hydrology model on the Ronne-Filchner basin, which includes one quarter of all ice in Antarctica and the second-largest ice shelf world-wide. The Ronne-Filchner basin exhibits sharp contrasts in subglacial topography, geology and hydrology, making it an interesting test case for the hydrology model. Furthermore, a sharp increase in sub-shelf temperatures under the Ronne-Filchner ice shelf has been suggested in coming centuries, yet this basin has been comparatively understudied thus far. We present projections under different warming scenarios and subglacial conditions, aiming to provide a sensitivity analysis of these different factors, and their interactions, on future sea level change. Our results provide insight on the importance of a detailed inclusion of subglacial geology and water evolution in large-scale ice sheet models.