Sensitivity studies for the Southern Ocean indicate that freshwater fluxes from various sources have a significant impact on the stability of the water column with consequences for sea ice and water mass characteristics. These sources are either atmospheric or result from ocean interaction with the base of Antarctic ice shelves and drifting icebergs. The resolution of global climate models does not allow for an adequate representation of the processes on polar continental shelves. Therefore, model deficits exist in terms of sea ice thickness, and water salinities and temperatures in regions important for the composition of the deep water participating in the global thermohaline circulation. In view of these deficits, Beckmann and Goosse [2003] parameterized the freshwater flux from major Antarctic ice shelf cavities in a global climate model calculating the net ocean-ice shelf heat flux as a combination of subsurface temperature at the continental shelf break and an effective basal area of melting. This study shows that a parameterization of the sub-ice freshwater flux is problematic because of the missing direct link to continental slope temperatures, major regional differences, and dependencies on the thickness of the shelf water column considered. Therefore, the only suitable way today might be prescribing the freshwater fluxes determined by regional coupled ice-ocean models like BRIOS at the southern boundary of large-scale global models corresponding to ice shelf fronts.