Characteristics of the Kuroshio in the vicinity of the Izu Ridge

Characteristics of the Kuroshio in the vicinity of the Izu Islands are analyzed by using hydrographic observations collected from 1938 to 1980 mostly by the Hydrographic Department, Maritime Safety Agency, Japan and by the Japan Meteorological Agency.It is shown that flow characteristics change as the Kuroshio approaches the Izu Ridge. 1) The position of the 10°C isotherm at the 500 m level, which is, an index of the position of the temperature front or of the current axis of the Kuroshio, is highly variable near the ridge. 2) The horizontal temperature gradient across the Kuroshio estimated from the positions of the 8 and 12°C isotherms across the Kuroshio decreases considerably near the Izu Ridge. 3) The horizontal distance between the 15°C isotherm at the 200 m level and 10°C isotherm at the 500 m level becomes larger over the ridge. The 15°C isotherm at the 200 m level is an index of the current axis at the sea surface. This implies that the inclination of the Kuroshio axis becomes larger over the ridge.