An interpretation of the bimodal character of the stable Kuroshio path

Abstract

The Kuroshio has two kinds of stable paths: (1) the so-called N-type without meander and (2) the so-called A-type with meander. A simple model based on the non-linear path equation explains the bimodal character in terms of bifurcation of the straight path and jumping of the solution from one branch to another. The Izu Ridge plays an essential role of limiting possible steady paths to those passing an assigned point at the downstream side. The reduction of the characteristic velocity of the Kuroshio leads to the disappearance of the N-type solution followed by a catastrophic transition to the A-type meander of large amplitude. The most important is that this dynamical system has the characteristic that small modification of the basic equation or consideration of realistic situation does not alter the nature of the bimodality of the Kuroshio path.