6. Sea Ice Thermodynamics

This chapter describes the physics of the sea ice thermodynamics beginning with basic assumptions and followed by a description of the fundamental equations, various parameterization, and numerical approximations. The philosophy behind the design of the sea ice formulation of CAM 3.0 is to use the same physics, where possible, as in the sea ice model within CCSM, which is known as CSIM for community sea ice model. The sea ice formulation in CAM 3.0 uses parameterizations from CSIM for predicting snow depth, brine pockets, internal shortwave radiative transfer, surface albedo, ice-atmosphere drag, and surface exchange fluxes. The full CSIM is described in detail in an NCAR technical note by Briegleb et al. [28]. The pieces of CSIM that are also used in CAM 3.0 (without the flux coupler) are described here.

The features of the sea ice model that are used in CAM 3.0 depend on the boundary conditions over ice-free ocean. If sea surface temperatures (SSTs) are prescribed, then sea ice concentration and thickness are also prescribed. In this case, the primary function of the sea ice model in CAM 3.0 is to compute surface fluxes. However, if the slab ocean model is employed, sea ice thickness and concentration are computed within CAM 3.0. These two types of surface boundary conditions within CAM 3.0 will be referred to as uncoupled and coupled in this chapter.