Multiple criticalities in coastal flows

Using a simple model, it is shown that a coastal current (composed of water of given dynamical structure) can occur in one of several different forms. The classification of these possible forms for the current is closely associated with the categorization of the behaviour of the various waves able to propagate along the coast. Among the forms of the current found are those differing in the criticality (direction of propagation) of long shelf waves as noted by Collings and Grimshaw, and the criticality of long Kelvin-waves as noted by Gill and Schumann. Earlier studies have considered these criticalities in isolation. The present study attempts to set them in a more coherent framework.