Internal Tide Transformation and Oceanic Internal Solitary Waves

Abstract

The transformation of internal tides, or long internal waves, as they propagate over the variable topography of the continental slope and shelf is discussed. Development of a model to describe this transformation is presented and is based on the Korteweg-de Vries equation. The model includes cubic as well as quadratic nonlinearity, dispersion, Earth's rotation and quadratic dissipation. An initial waveform, described in terms of a vertical modal function that is periodic in time, propagates through an environment of slowly varying water depth and stratification. The role of cubic nonlinearity and the Earth’s rotation are examined in detail using idealised conditions. Observations are presented from the Australian North West Shelf of a variety of strongly nonlinear internal waves. Numerical solutions to the KdV model are also provided for observed conditions and model predictions are compared to observations.