A Geostrophic Adjustment Model of a Tidal Mixing Front

Abstract

This paper presents a model of a tidal mixing front as occurring between well mixed and (seasonally) stratified water in tidally energetic areas in continental shelf seas. The model examines the geostrophic adjustment of a stratified two-layer fluid and a homogeneous fluid of intermediate density, originally separated by a vertical barrier The frontal position and shape, as well as the velocity distributions in the final equilibrium state are determined by three physical parameters: a density ratio, a layer depth ratio and a baroclinic radius of deformation. Solutions are presented for a number of parameter values. It is shown that only one-third of the potential energy released during the adjustment process is converted into kinetic energy. A number of previously studied adjustment problems have been reexamined, and it appears that the energy conversion factor equals ⅓ in an the considered cases, irrespective of the geometry. It is suggested that some general energy conversion property exists which is likely to be associated with the assumption of potential vorticity conservation during the adjustment process.