On the Parameterization of Basal Heat Flux for Sea-ice Modelling

A sea-ice model is used to investigate the ice-ocean heat flux that occurs at the base of the ice. The source of this basal heat flux is supposed in reality to arise from physical processes (e.g. oceanic mixed-layer entrainment, ocean advection, or solar heating in leads) which elevates the mixed-layer ocean temperature above the in situ freezing point and thereby causes a flow of heat from the mixed-layer to the base of the ice. In this study a dynamic-thermodynamic sea-ice model is coupled to a slab ocean model and forced with monthly climatological atmospheric forcing. The model domain is the Arctic Ocean and the neighbouring seas but the focus of the study is the area of perennial Arctic ice away from the marginal ice zones. The question asked, in the context of global climate modelling, is how sensitive is the sea-ice cover to the manner in which the basal heat flux is parameterized. Two numerical experiments are performed using (i) first a procedure in which heat is fluxed from the ocean to the ice using a turbulent transfer parameterization and (ii) secondly a simpler scheme in which heat is transferred instantaneously from the ocean to the ice. The conclusion is that for application in global climate models the simplified scheme (with instantaneous transfer) works satisfactorily. A discussion of the details of the differences in the simulated sea ice for the two experiments is also presented