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The usefulness of the concept of JEBAR, the joint effect of baroclinicity and relief, in large-scale ocean dynamics is critically analyzed. The authors address two questions. Does the JEBAR term properly characterize the joint impact of stratification and bottom topography on the ocean circulation? Do estimates of the JEBAR term from observational data allow reliable diagnostic calculations? The authors give a negative answer to the first question. The JEBAR term need not give a true measure of the effect of bottom relief in a stratified ocean. A simple two-layer model provides examples. As to the second question, it is demonstrated that the large-scale pattern of the transport streamfunction is captured by the smoothed solution, especially with the Mellor et al. formulation of the JEBAR term. However, the calculated velocity field is very noisy and the relative errors are large.

The effect of bottom topography H on the barotropic transport in a periodic zonal channel is studied. An asymptotic approximation is found for the zonal transport on anf-plane and a P-plane when all f/H isolines are blocked by the zonal walls. It is shown that to leading order, the zonal channel transport is independent of friction. In this it is similar to the Sverdrup transport in a basin. To leading order, the transport is proportional to the bottom topographic wavelength, and inversely proportional to the height of the topography and to R, the range of values of f/H that exists on both sides of the channel. For sufficiently high topography the transport varies inversely with the topographic height squared. The analytic results are verified by numerical experiments.

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The behavior of the solution to a two-layer wind-driven model in a multiply connected domain with bottom topography imitating the Southern Ocean is described. The abyssal layer of the model is forced by interfacial friction, crudely simulating the effect of eddies. The analysis of the low friction regime is based on the method of characteristics. It is found that characteristics in the upper layer are closed around Antarctica, while those in the lower layer are blocked by solid boundaries. The momentum input from wind in the upper layer is balanced by lateral and interfacial friction and by interfacial pressure drag. In the lower layer the momentum input from interfacial friction and interfacial pressure drag is balanced by topographic pressure drag. Thus, the total momentum input by the wind is balanced by upper-layer lateral friction and by topographic pressure drag. In most of the numerical experiments the circulations in the two layers appear to be decoupled. The decoupling can be explained by the JEBAR term, whose magnitude decreases as interfacial friction increases. The solution tends toward the barotropic one if the interfacial friction is large enough to render the JEBAR term to be no larger than the wind stress curl term in the potential vorticity equation. The change of regimes occurs when the value of the interfacial friction coefficient equals 0 ϭ H 1 f 0 (L y /L x)(A/H 0), where f 0 is the mean value of the Coriolis parameter; L y and L x are the meridional and zonal domain dimensions; H 0 and H 1 are the mean depths of the ocean and of the upper layer; and A is the amplitude of topographic perturbations. Note that 0 does not depend on the strength of the wind stress. The magnitude of the total transport is found to depend crucially on the efficiency of the momentum transfer from the upper to the lower layer, that is, on the ratio /, where is the lateral friction coefficient. If and are assumed to be proportional, the upper-layer transport and total transport vary as Ϫ5/6 .