Ocean circulation under idealized conditions and effects of meso-scale eddies

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In order to understand the ocean circulation dynamics in idealized configurations, we carried out the following three studies.1.Ocean circulation in an eddy-resolving model-Adopting a two-layer quasigeostrophic model driven by anti-symmetric Ekman pumping, a numerical solution with double eastward jets which are prematurely separated from the western boundary was obtained when the inertial boundary layer thickness is realistic and viscous western boundary layer is not very thin, as well as a solution with a single eastward jets along the inter-gyre-boundary. The latitude of the eastward jet of double-jet solution is insensitive to parameters, and strongly depends on the meridional profile of the wind forcing. A parameter region where both the single-jet and double-jet solutions coexist was found.2.Upper-layer ocean structure in an idealized ocean GCM-" Focusing on the mixed-layer depth (MLD) front, we investigated the MLD distribution and subduction of low PV water. It was found that the MLD front occurs along a curve where the upper-layer geostrophic current flows parallel to outcrops. The water subducted at the MLD front does not cross the outcrop, different from that expected from the ventilated thermocline theory. The effect of seasonally variable forcing on the MLD distribution was also investigated.3.Effects of bottom topography: It was found that the mass transport of a western boundary current over a slope in high latitude almost coincides with the annual mean Sverdrup transport in a weak wind season, while it coincides with instantaneous Sverdrup transport in strong wind season, if we define the transport as the integrated current from the coast to a point where the current direction changes. Rossby waves over a one-dimensional periodic topography were also investigated.