Interactions between internal gravity waves and their traumatic effect on a continuous stratification

Abstract

An investigation is made of the detailed kinematic conditions which characterize ‘breaking’ of internal waves in a continuous density field. It has been observed that ‘breaking’ is associated with localized, abruptly appearing intensifications of the density gradient. Turbulence subsequently develops from these intensifications or ‘traumata’.

Interactions between two or more disparate waves produce distortions more extreme than would be deduced from linear combination. This is exploited experimentally by crossing two weak internal wave beams from separate sources.

Lagrangian integration of the motion field defined by the beams gives extrema of isopycnic slope, Richardson number defined by shear across isopycnics and dynamic vertical density gradient, and dynamic density gradient, under conditions for the appearance of traumata.