John Reilly: Idealised Ice-Ocean Coupling Evaluation
Interactions between Antarctic ice shelves and the ocean regulate basal melting, ice-shelf buttressing, grounding-line migration and ice discharge. Yet these feedbacks are represented incompletely: ice-sheet models typically prescribe basal melt, while ocean models often use fixed or prescribed ice-shelf geometry. Closing this feedback loop is necessary to represent how ocean-driven melting modifies cavity geometry and ice flow, and how those changes reorganise ocean circulation and melting.
We present an initial two-way coupled configuration of the Ice-sheet and Sea-level System Model (ISSM) and Modular Ocean Model 6 (MOM6), implemented within the Australian Community Climate and Earth System Simulator (ACCESS) framework. Coupling is enabled through the National Unified Operational Prediction Capability (NUOPC). The system exchanges evolving ice geometry and grounding information from ISSM to MOM6, and ocean-computed basal melt from MOM6 to ISSM through a mediator.
We evaluate the capability using the hierarchy of idealised experiments defined by the MISOMIP1 protocol. Idealised ice-only simulations test grounding-line retreat and re-advance under prescribed melt scenarios; idealised ocean-only simulations test MOM6 beneath prescribed evolving ice-shelf geometries; and early coupled ice-ocean simulations exercise the complete coupled feedback loop. We present protocol diagnostics spanning ice geometry, grounded area, volume above flotation, cavity circulation, ocean thermal structure and basal melting.
Together, these experiments demonstrate an ACCESS-compatible pathway to coupled simulations with evolving cavities and grounding lines. This capability supports verification and feedback studies, future regional Antarctic applications, and integration of an interactive ice-sheet component into the Australian Earth System Model.