Breaking of Super-Critically Incident Internal Waves at a Sloping Bed

A laboratory experiment was carried out to investigate the mixing on a sloping bed caused by a localised ray of internal waves breaking with super-critical frequencies. Previous work has shown that for near critical waves the turbulent boundary layer was confined to a thin region just above the bed. As a result, relatively small overturning turbulent lengthscales were observed. On the other hand, larger turbulent lengthscales and more mixing occurred at moderately super-critical waves, consistent with some earlier laboratory results. Calculation of the energy budget of the incident and reflected wave rays showed the vertical diffusivities as high as 10-4 m2 s-1 observed in field studies could be realised by the internal wave breaking process at the boundaries.