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Ocean General Circulation Model

The ocean GCM, Poseidon V4 (Schopf and Loughe, 1995; updated to include prognostic salinity as in Yang et al., 1999), is designed with generalized horizontal and vertical coordinates including an embedded turbulent surface mixed layer parameterized according to Kraus-Turner and implemented following Sterl and Kattenberg (1994). The interior layers are treated in a quasi-isopycnal fashion in which layers do not vanish at outcrops, but retain a thin minimum thickness at all grid points. Exchanges between layers tend to maintain the target densities on a specified timescale. Horizontal mixing within the model is implemented with high order Shapiro filtering. Vertical mixing and diffusion are parameterized using a Richardson number dependent scheme of Pacanowski and Philander, enhanced for layers within the mixed layer and within the water column where the inferred density profile is gravitationally unstable. Shortwave radiation penetrates below the ocean surface, with penetration depth provided from a SeaWiFS climatology of kpar. A thermodynamic sea-ice model, following Hakkinen and Mellor (1992) is included, with heat and freshwater exchange to the first layer of the ocean model. The equations are solved implicitly.