Internal wave induced dispersion and mixing on a sloping boundary

A fluorescent dye‐tracer was released in a stratified water column above a sloping boundary revealing profound dispersive asymmetry. Initially the dye spread symmetrically in the vertical until the deeper portion became influenced by the bottom boundary layer (BBL). The shallower portion then spread rapidly up‐slope in a thin boundary layer influenced by highly non‐linear isopycnal distortions. The deeper, down‐slope portion of dye subsequently became detached from the boundary and intruded into the basin interior in three distinct layers along isopycnal surfaces. The intrusions result from the gravitational collapse of mixing patches created by baroclinic flow over an irregular boundary. The vertical separation of the layers matches the inverse topographic wavenumber. Up‐slope displacement of the dye is consistent with an advective/diffusive balance near the sloping boundary, controlled by slope angle and roughness. Horizontal diffusivities increased from 1.4 m2s−1 to 18.4 m2s−1 during the 4‐day experiment.