A protocol for calibrating basal melt rates in the ISMIP7 Antarctic ice sheet projections

Abstract. Ocean-driven melting at the base of the floating ice shelves of the Antarctic Ice Sheet is an important driver of current and future ice losses. Ocean models that resolve sub-shelf melt rates at sufficient resolution are too expensive to run in large ensembles or for multi-centennial projections. Instead, ice-sheet models use simple modules to infer sub-shelf melt rates based on far-field ocean properties. However, there is no consensus on the optimal set of parameters for these modules. Here, we present a protocol for ice-ocean interactions in ISMIP7 Antarctic Ice Sheet projections. We describe (1)~how CMIP model datasets are processed to be used in melt modules, (2)~how parameters in melt modules can be selected to be physically constrained by oceanographic knowledge, (3)~the rationales for a range of datasets that span possible evolution of the Southern Ocean between 1950 and 2025, (4)~design for a melt Module Intercomparison Project (meltMIP) that will allow us to better assess uncertainty in sea level projections related to melt modules. Finally, we summarise lessons from ISMIP7 and potential research directions towards the next generation of ice-ocean interaction modelling.