Preface Large amplitude internal waves in the coastal ocean

The flow in the coastal ocean, and especially on the continental shelf and slope is often characterized by the presence of very large-amplitude internal waves.These are waves which occur in the interior of the ocean, and propagate horizontally with a concentration of their energy around the oceanic pcynocline.They are usually generated by the interaction of the barotropic tide with the shelf break, topographic sill or with other prominent bottom features.This leads to the formation of an internal tide, which then deforms and evolves into a train of very large-amplitude internal waves, with associated large pycnocline displacements and strong currents.They are highly significant for sediment transport and for the biology on the continental shelf, their associated currents cause strong forces on marine platforms and submersibles, the associated strong distortion of the density field has a severe impact on acoustic signaling and their capacity to break and form microstructure has major consequences for the understanding of interior ocean mixing.It is now well established that the observed waves can be understood as internal solitary waves, or as internal undular bores, and to a first level of understanding can be modeled by the Korteweg-de Vries (KdV) equation, or by one of various extensions, see the reviews by Grimshaw (2001Grimshaw ( , 2010) ) and Helfrich and Melville (2006).While these models form the basic paradigm, there remain several outstanding issues which are of current concern.These include estimating the effects of shear-induced instability, a need to go beyond the weakly nonlinear KdV models and study finite-amplitude waves, the effect of background rotation, transverse effects induced by topography, and the need to go beyond the single