A dynamical system for classifying buoyant coastal discharges

Buoyant discharge into the coastal ocean occurs in a confusing variety of forms and scales. In this paper I offer a classification system for such discharges based on scaling analysis of the continuity and momentum equations. The approach is phenomenological, as the principal flow scales must be known a priori. The primary parameter that emerges is the Kelvin number K, the ratio of the buoyant structure width to the baroclinic Rossby radius. Two limiting cases, K small and K large, are readily understood from the scaling analysis. I arrange 12 examples of buoyant coastal discharge observations into a hierarchy in K. Those for the smallest K have the properties predicted by the small K limiting case: strong advection terms and Froude numbers of order unity, but small Coriolis effects. Those for the largest K correspond well to the large K limiting case: weak advection terms, small Froude numbers, but order one Coriolis terms. The classification system should be useful for interpreting both future observations and model results.