| Summary: | Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution July 1993 In this thesis, the dynamic role of bottom topography in a β-plane channel is systematically studied in both linear homogeneous and stratified layer models in the presence of either wind stress (Chapters 2, 3, 4, and 6) or buoyancy forcing (Chapter 5). In these studies, the structure of the geostrophic contour plays a fundamental role, and the role of bottom topography is looked at from two different angles. It is shown that blocking all the geostrophic contours leads to two different physical processes in which bottom topographic form drag is generated (Chapters 2, 3 and 4) and enables geostrophic flow in a β-plane channel to support a net cross-channel volume transport (Chapters 5 and 6). It is demonstrated that by blocking all the geostrophic contours in the presence of a sufficiently high ridge, the dynamics of both source-sink and wind driven circulations in a β-plane is similar to that in a dosed basin. First, wind-driven circulation in the inviscid limit is discussed in a linear barotropic channel model in the presence of a bottom ridge. There is a critical height of the ridge, above which all geostrophic contours in the channel are blocked. In the subcritical case, the Sverdrupian balance does not apply and there is no solution in the inviscid limit. In the supercritical case, however, the Sverdrupian balance applies. The form drag is generated through two different physical processes: the through-channel recirculating flow and the Sverdrupian gyre flow. These processes are fundamentally different from the nonlinear Rossby wave drag generation. In this linear model, the presence of a supercritical high ridge is essential in the inviscid limit. With this form drag generation determined, an explicit form for the zonal transport in the channel is obtained, which shows what model parameters determine the ...
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