Lateral wave breaking and 'shingle' formation in large-scale shear flow.

Abstract

The temporal evolution of large amplitude quasi geostrophic disturbances in a piecewise uniform potential vorticity flow was elucidated by numerical solutions of the 'contour dynamical' equations. Lateral wavebreaking occurs when the initial disturbance amplitude exceeds a certain value, and at later times tongues of the lower vorticity fluid are engulfed or entrained into the higher vorticity shear flow. The effect appears to be important for the evolution of 'shingles' observed between the coastal water and the cyclonic side of the Gulf Stream. The effect may also be an important phase in initiating the mixing process at the perimeter of an eddy embedded in another water mass. (A)