THE DYNAMICS OF BAROTROPICALLY DOMINATED RINGS

Based on observations, the proposition is forwarded that some rings in volve important deep flow. The work described herein is directed at un derstanding the consequences on eddy evolution of such structure. An a nalysis of the equations of motion is conducted that emphasizes the im portance of the lower layer evolution. The thermocline responds in a l argely passive fashion. This analysis differs considerably from previo us theories, which focus on the evolution of surface-intensified rings . The most important practical differences are that the coupled system can be expected to exhibit propagation in any direction (as opposed t o predominantly west, as in reduced gravity theories), and that the pr opagation rates dan be an order of magnitude greater than those of red uced gravity systems. These aspects of the present analysis are in acc ord with many ring observations. A series of primitive equation numeri cal experiments are conducted to test these ideas, with the result tha t the experiments support such ''barotropically dominated dynamics'' a s a useful qualitative and quantitative tool for the study of eddies a nd rings. The asymptotic analysis also suggests that initial condition s with closed regions of potential vorticity should differ significant ly from those with no closed potential vorticity zones. This hypothesi s is supported by primitive equation inns; approximately compensated l ower-layer experiments (with no closed potential vorticity contours) e xhibit qualitatively and quantitatively different behavior than experi ments with initially energetic lower layers (which have closed potenti al vorticity contours).