Earth System Models (ESMs) have played an important role in projections of ice sheet mass loss by providing the boundary conditions for Ice Sheet Models (ISMs). Two-way coupling of ISMs within ESMs presents new opportunities for ice sheet projections while capturing feedbacks between the climate and ice sheet mass balance. Simulating Antarctic Ice Sheet evolution presents unique challenges in an ESM including high sensitivity to ocean thermal forcing and potentially rapid and extensive grounding line retreat. Here we present simulated ice-ocean interactions at Antarctic ice shelves in the Energy Exascale Earth System Model (E3SM). We show that grounding line retreat and cavity geometry evolution can be produced dynamically in the ocean component of E3SM from changes in ice sheet mass via a pressure boundary condition on the ocean surface. This contrasts with the common coupling strategy of imposing ice-sheet geometry changes from an ISM on the ocean component, necessitating ad hoc modifications to the ocean state. One of the benefits of our approach is a consistent treatment of inundation in both coastal and ice sheet settings. We present simulation results in a regional configuration of the ocean component of E3SM; future work includes global E3SM simulations fully coupled with the ice sheet component, MPAS-Albany Land Ice (MALI).