Geostrophic current velocities

The estimates of the climatic mean annual parameters of the MRC in the sections normal to the northeastern coast of the Black Sea presented in [17] yielded a distance of its core from the shore about 40 km, a full width of the current (with respect to velocity values of 0.02 m s-1) of 75 km, a penetration depth of 275 m, a maximal geostrophic velocity of 0.31 ms-1, and a volume transport of 1.3 x 106 m3 s x. These estimates are of the same order of magnitude as shown in Fig. 4a within the velocity interval to 0.20 m s x. This allows us to suggest a certain geographical universality (self-similarity) of the MRC profile normal to the coast. 

It is illuminating to study the time evolution of a river plume as an initial value problem. It can be shown that the current pattern is governed by a geostrophically adjusted eddy confined to the buoyancy patch (near field) and a coastally trapped flow that develops in the wake of a Kelvin wave (far field). Behind the front of the first Kelvin wave mode, undercurrents are set up. Although the velocities of the flow forced by the momenrnm of the river mnoff are small enough to justify a linear treatment, there are important nonlinear effects owing to the advection of density, which limits the validity of the linear analytical models. In particular, the structure of the near field in front of the river mouth is dominated by the response to the buoyancy flux associated with the river discharge. 

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