Dynamics of Internal Gravity Waves in the Ocean

Abstract

7R59. Dynamics of Internal Gravity Waves in the Ocean. - YZ Miropol’sky (PP Shirshov Inst of Oceanology, Russian Acad of Sci, Moscow, Russia). Kluwer Acad Publ, Dordrecht, Netherlands. 2001. 406 pp. ISBN 0-7923-6935-1. $149.00. Reviewed by O Phillips (Dept of Earth and Planet Sci, Johns Hopkins Univ, Charles and 34th St, Baltimore MD 21218-2681).Internal gravity waves occur in the atmosphere and oceans as a result of their internal density stratification. In the atmosphere, the flow is sometimes visualized naturally by rows of cloud bands, condensation regions near the wave crests. In the oceans, they have excited intense interest because of their strong effects on acoustic propagation. To a fluid mechanician, they offer a beautiful array of phenomena, mostly as a consequence of their anisotropy (the restoring force in the oscillation, gravity, acts only vertically). These waves can be demonstrated vividly in simple laboratory experiments; their phase and group velocities are orthogonal, their frequency range is bounded, their wavelength changes on reflection from a sloping bottom, and when the stratification varies in the vertical, there can be internal trapping and things like that. This beautiful book, a graduate-level text and reference, is a poignant epitaph to its young author, whose premature death has saddened his many intellectual colleagues throughout the world. Its development of the basic dynamical theory is clear and comprehensive, starting with the linear theory of propagation in a horizontally homogeneous, but vertically stratified medium that is otherwise at rest. It continues by inclusion of horizontal shear with the possibility of critical layers, and proceeds to discussion of horizontal inhomogeneities. Internal waves seem to be generated ubiquitously in nature. A number of generation mechanisms are known, but as Miropol’sky freely admits, there are still a few things to be understood here. The Hamiltonian formulation for weak nonlinear fields, solitons, and resonant wave interactions lead to two short but informative chapters on ocean measurements and laboratory experiments. The qualities of this book remind us of why the author was regarded as one of the brightest leaders in this area of fluid mechanics. It is written comprehensively and authoritatively, with clarity and grace. It is, in places, demanding of the mathematical skills of the reader, but only when necessarily so. The line diagrams are fine, but it might have been helpful to have had a few good photographs of some pivotal experiments, such as there are in JS Turner’s book, Buoyancy Effects in Fluids. The translation by OD Shishkina is excellent—smooth and accurate. It is probable that here we may have a new classic in the field and, though the price is a bit steep, Dynamics of Internal Gravity Waves in the Ocean should be in the library of every serious fluid dynamicist and dynamical oceanographer or meteorologist.