Sack Lunch Seminar (SLS)

Eddy mixing in the ocean is regulated by dissipation of external mechanical energy. Traditionally, eddy mixing in the ocean is treated as the diapycnal (vertical) mixing and lateral mixing. The common wisdom in oceanography is that lateral mixing takes place along isopycnal surfaces, but no solid reasoning or theoretical analysis has been presented why mixing should be along isopycnal.
A variation principle is postulated: the preferred direction of lateral mixing in the ocean should be the direction along which the gravitational potential energy released during eddy mixing is maximal; this direction is called the natural direction (slope) for lateral mixing in the ocean. This postulation is applied to the circulation and water mass properties in the world ocean. In most places, the natural slope is approximately half the slope of the isopycnal surface. This study suggests that a new generation of oceanic general circulation model should be developed which can handle the eddy mixing in the ocean more accurately.