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Coupling

The land/ocean mask for the coupled model is defined on the ocean's latitude-longitude grid, so each grid box is either all ocean or all land. The atmosphere to ocean couplers interpolate from the atmospheric grid to the mass point of the underlying ocean boxes using bilinear interpolation (e.g., Vintzileos and Sadourny, 1997). In the ocean to atmosphere coupling, interpolation consists of averaging together the underlying ocean grid boxes. Fluxes are exchanged on a daily basis. The coupling between the land and the atmosphere is handled in a similar fashion. The CGCM runs without any flux correction.

The ocean model controls the evolution of all non-land surfaces, i.e., open ocean, shallow seas and sea ice. Inland lakes are treated by the atmosphere as land surfaces.

The ocean domain extends from Antarctica to 72°N. There is a 10°-wide buffer zone at the northern boundary in which the temperature, salinity and layer thickness are relaxed to climatological fields derived from the World Ocean Atlas 1997 (Levitus, 1994). From the northern boundary to the North Pole, a slab ocean “mixed layer” model, with sea-ice enabled, is used merely for heat exchange with the atmosphere. This approach is also used for shallow seas and the continental shelves.