A numerical model of the development of anticyclonic circulation in a gulf-type region of freshwater influence

This paper concerns gulf-type regions of freshwater influence (ROFIs). In these, the width of the channel or gulf into which freshwater discharges is greater than the internal Rossby radius of deformation, so rotation is important, but not so much greater that the plume behaves as if discharging along a straight, coast with no effect of the boundaries In these circumstances, there are reports of anticyclonic circulation in the stratified water at the head of the gulf, which can be strong enough to deflect the river, plume from its expected turning direction it leaves the river mouth. A recent paper by Fujiwaraet al. (1997), postulates divergence in the upper layer due to entrainment, in an estuarine circulation as the source of this anticyclonic circulation. we suggest that the area of freshwater stratification near the river mouth, forming the bulge of a typical river, plume in a low friction, low entrainment case, can readily form a persistent region of anticycyclonic circulation. This can then affect the direction of subsequent discharges, as the outflow varies in time. This is demonstrated by a numerical model of discharge into a rectangular gulf: