| description abstract | Numerical experiments are executed using a two-layer inflow?outflow ocean model with simplified geometry to investigate the effects of stratification and bottom topography on the path variation of the Kuroshio south of Japan. In a flat-bottom ocean, the dependence of the Kuroshio path selection on its inflow velocity Vmax is basically the same as in a barotropic ocean, that is, the Kuroshio takes a straight path at low Vmax (regime I), a meandering path at high Vmax (regime II), and both paths at intermediate Vmax (regime III: multiple equilibrium state). However, the range of regime III shifts to higher Vmax by 0.10?0.30 m s?1. Stratification causes and maintains the offshore shift of the current path south of Kyushu through the conservation of potential vorticity. As a result, a small meander stagnates southeast of Kyushu, not developing into a large meander even for higher Vmax since the vorticity supply from the coast is reduced. For the same reason, higher Vmax is needed to maintain a meandering path. Bottom topographic features such as a continental slope and ridge significantly change the path selection. A straight path appears for the whole experimental range of Vmax and a meandering path only exists at intermediate Vmax. The continental slope along the southern coast of Japan captures the main flow to permit a straight path for all Vmax. Further, the Izu Ridge inhibits a meandering path hanging over the western flank of the ridge and narrows the range of Vmax in which the meandering state exists. The transition induced by monotonic changes of Vmax is significantly affected for a jump from a straight to a meandering path but not affected as much for a reverse jump. In a flat-bottom ocean, the enlargement of a small meander due to baroclinicity causes a quick transition from a straight to a meandering path with a large velocity change while the transition is impeded for a small velocity change. No transition occurs by a monotonic increase in Vmax with bottom topography since a straight path can exist for all Vmax. | |
