Western Boundary Current Crossing a Ridge:Barotropic and Equivalent Barotropic Models

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Investigated is a possibility of two-dimensional model in the study of the dynamics of the western boundary current by a numerical experiment. Emphasis is laid on the effect of bottom barrier corresponding to the Izu Ridge.<BR>The western boundary current in the model is formed by source and sink of the water prescribed at an artificial eastern wall (600km offshore). The bottom topography consists of a continental slope parallel to the straight western coast, and a ridge protruding from the western coast to 500km offshore (1, 500m deep and 400km wide). The grid size of 12km×25km (offshore and longshore directions, respectively) resolves both the western boundary current and the bottom topography.<BR>The assumption of homogeneity of the water density makes the western boundary current detour along the isobath of the ridge.<BR>A steady state solution is obtained under the assumptions that the horizontal velocity does not change direction vertically (equivalent barotropic), and that the geostrophic relationship holds at the bottom. Homogeneity of the water density is not assumed. The solution shows that most of the volume transport of the western boundary current cross the ridge and the current has cyclonic vorticity near the summit of the ridge. It seems to suggest that the investigation by three-dimensional models is neccesary in order to study the complete dynamics of the western boundary current crossing the ridge.
日本海洋学会の論文