Ocean models in climate problems

Abstract

Ocean climate models are reviewed, with emphasis on modelling large-scale ocean-atmosphere interactions. Feedbacks between the thermohaline circulation and atmospheric transport processes are discussed, and how they can be represented in ocean-only models through careful choices of the surface boundary conditions. A theoretical analysis of large-scale air-sea heat exchanges is presented, together with a possible implementation into a numerical model through surface thermal boundary conditions. Proper representation of large-scale freshwater exchange between ocean and atmosphere requires an explicit model of atmospheric moisture transport; an example is presented in which the interaction of the atmospheric hydrological cycle with the thermohaline circulation destabilizes the thermohaline circulation. Multiple equilibria, corresponding to fundamentally different climate states, and internal low-frequency variability of the thermohaline circulation have been found in numerical models and are reviewed. -from Author