A simple laboratory model for the oceanic circulation

Abstract

A linear theory is developed for the motion of a viscous, incompressible fluid in a rotating cylinder with a sloping bottom. An analysis of the normal modes of oscillation reveals that the presence of the bottom slope introduces a new set of low frequency inertial oscillations to replace the purely geostrophic modes which are not allowed in this geometry. The new waves possess mean circulation and are the mechanism by which the fluid adjusts to changes in the rotation rate of the container, a process discussed in detail. The steady motion produced in the cylinder when the cylinder's upper surface rotates at a different rate than the bottom surface is studied. It is shown that the presence of the bottom slope inhibits the steady fluid motion in the body of the cylinder and introduces a non-symmetric, high velocity side wall boundary layer. Experimental evidence, presented to validate the theory, reproduces certain important features of the oceanic circulation.