Dynamics of the Kuroshio large meander

The bimodality of the Kuroshio path is studied numerically with a barotropic inflow-outflow model. The dynamics that determines the path depends on the Rossby number,Ro (proportional to inlet velocity) and the Reynolds number (representing effects of viscosity). At lowRo (<Ro₁) only a meander path occurs, while at highRo(Ro₂) only a straight path is developed. Between these critical values (Ro₁RoRo₂) either of the two paths can occur (multiple states), and the choice of path is determined by its history. Increase (decrease) inRo acrossRo₂ (Ro₁) leads to catastrophic transition from one path to the other. In the intermediate range (Ro₁RoRo₂), the straight path is conditionally unstable to finite amplitude disturbances, and abrupt changes to the meander path take place. Absolute vorticity is almost conserved along the meander path, while along the straight path it is dissipated in large amount near the coast. At low Re, the flow tends to a viscous flow, and steady states are obtained. At highRe, time variations with different periods for the meander and straight paths become dominant. Intermittent transitions from one state to the other without any changes of external parameters are found at intermediateRo and at highRe.