Internal Waves

Internal waves are a ubiquitous feature in the ocean. They are of considerable importance in the marine environment as they can both create currents and drive turbulent ocean mixing. Nonlinear internal waves (NLIWs) or solitons induce large vertical displacements of constant density (isopycnal) surfaces of O(100 m) and strong horizontal velocities of O(1–2 m/s) as they propagate. Such large displacements and velocities, in turn, affect nutrient mixing and biological productivity, sediment resuspension, the propagation of acoustic waves, and marine and offshore engineering operations. As NLIWs are potentially hazardous to subsea oil and gas operations, the ability to predict the occurrence and arrival of these waves is necessary for both cost-effective operation and safety. Despite the considerable body of knowledge about these waves, the prediction of NLIWs remains a very challenging issue and the subject of ongoing research. This article first discusses the theory of internal waves. It then focuses on the generation, propagation, and dissipation of internal tides. Finally, it considers the implications of internal tide dynamics for engineering design and operation in the offshore environment.