SURFACE FRONTS IN ESTUARIES - A REVIEW

Recent advances in the understanding of the physics of estuarine fronts (small-scale regions of significant changes in hydrographic variables) are reviewed. These fronts may be classified in three groups-tidal mixing fronts, plume fronts, and shear fronts-on the basis of the mechanism dominating the local rate of change in the horizontal density gradient. These classes are not independent, however, since it appears that both tidal mixing fronts and shear fronts can produce buoyancy-driven flow structures that propagate away from the generation region as plume fronts. Field observations of typical examples of each class are presented and laboratory experiments and theoretical models which isolate the important physical processes are summarized. Some important unresolved questions are identified and suggestions for further research are offered.