Effects of Stratification and Bottom Topography on the Kuroshio Path Variation South of Japan. Part II: Path Transitions in a Multiple Equilibrium Regime

Abstract

Abstract The effects of stratification and bottom topography on the Kuroshio path transitions in a multiple equilibrium regime due to a short-term velocity increase are examined using a two-layer inflow–outflow model with simplified coastal geometry and bottom topography. For an imposed velocity increase on a straight-path state, the typical transition from a straight to a meandering path occurs with or without bottom topography through the same process as in a barotropic case with flat bottom. Thus, the geometrical effect of Kyushu is essential to this transition or to the formation of a small meander triggering the transition; stratification and bottom topography are somewhat secondary. Nevertheless, under the influence of stratification, a small meander significantly develops south of Kyushu during a decreasing phase of velocity through shoaling of the interface depth and triggers the transition with the amplification rate of velocity Amp of 1.5. The continental slope south of Japan prevents a small me...