Residual Circulation, Mixing, and Dispersion

Abstract

This chapter covers tidally averaged circulation, salinity structure, and dispersion in estuaries. It begins with a discussion of volume and salt conservation for full estuarine systems. This leads to a focus on volume and salt fluxes through a cross section near the estuary mouth. Techniques for calculating various parts of these fluxes are reviewed, leading to the classical ‘exchange’ and ‘tidal’ parts of the up-estuary salt flux. A simple description of the physics leading to the exchange flow is given, with some discussion of the many factors ignored in its derivation. Tidal salt flux is then discussed, somewhat more informally, with comments on along-channel dispersion. Along the way, we use specific examples from observations and numerical simulations. There is a bias toward our own work in US Pacific Northwest estuaries, but, hopefully, we have indicated some sense of the scope of work globally.