The Slab Ocean Model (SOM) configuration enables a simple but tightly coupled ocean modeling component combined with a thermodynamic sea ice component based on the CCSM3 sea ice model. This configuration of the atmospheric model allows for a fully-interactive treatment of surface exchange processes in the CAM 3.0. The ocean prognostic variable is the mixed layer temperature , while the thermodynamic sea ice model treats snow depth, surface temperature, ice thickness, ice fractional coverage, and internal energy at four layers for a single thickness category. The ocean mixed layer contains an internal heat source (also called a flux), whose values are generally specified by a CAM control run, representing seasonal deep water exchange and horizontal ocean heat transport. For example, using prescribed sea surface temperatures and sea ice distributions, the net surface energy flux over the ocean surface can be evaluated to yield the heat source . Additional exchange of heat occurs between the ocean mixed layer and the sea ice model during ice formation and ice melt. To ensure the CAM 3.0 SOM sea ice simulation compares well to the observed ice distribution, and to moderate sea ice changes in climate change experiments, the flux term is adjusted under the ice in a globally conserving manner.