Estimates of turbulent diffusivity across the S. Atlantic based on a parameterization for
mixing by internal tide energy. The section spans from west to east across the Brazil and Angola
Basins. The shaded topography follows the deepest bathymetry of the Mid Atlantic Ridge system, while
the upper contour shows the shallowest level of Ridge topography. The apexes of the Mid-Atlantic
and Walvis Ridges are apparent at 15°W and 5°W, respectively (St.
Laurent, Simmons, and Jayne 2002 
).
Models of the ocean circulation, and of the Earth’s climate, involve numerical solutions to the dynamical equations for momentum, heat and energy. Due to the computational complexity of this task, these equations are typically limited to describing only a subset of the full problem. In particular, temporal resolution is often limited to time-scales longer than about a day, and spatial-scales of about 10 km. Processes occurring on shorter time or spatial scales, such as internals waves, tidal processes, or turbulent mixing, must be incorporated into these models using a method of representation known as parameterization. The unresolved processes are represented by formulas involving parameters that govern the resolved flow. These formulas are derived using results from measurement, theory, and modeling.