Boundary–interior exchange: Reviewing the idea that internal-wave mixing enhances lateral dispersal near continental margins

Near-boundary mixing affects the dispersal of seawater constituents and may have important consequences for ecological and geological processes since continental boundaries are a fundamental source of lithogenic sediments, nutrients, iron and carbon. This paper examines the idea that gravitational collapse after near-boundary vertical mixing events leads to enhanced dispersal in the horizontal (along-isopycnal) direction. Dye studies from the continental shelf and laboratory investigations of intrusions generated by internal-wave breaking suggest that this is a viable mechanism for offshore dispersal of boundary-layer fluid. However, there have been few attempts to examine this process in the ocean or to quantify it in a form amenable to parameterization. Here this process is considered primarily for continental slopes and conditions of relatively uniform stratification, rather than for shelves where the boundary can intersect a front or seasonal thermocline. This paper reviews a selection of studies examining this concept in the laboratory and ocean, and reviews studies linking internal-wave reflection and mixing to the offshore dispersal of suspended sediment from continental margins.