Warm Water Regions off Shikoku Associated with the Kuroshio Meander

Abstract

   There has always been seen a warm water region south of the Kuroshio off Honshu. It is located off Shikoku or Tokaido, according to whether the Kuroshio takes a path with or without meander. These warm water regions have lens-shaped thermostads in the subsurface layer above the main thermocline, which have a thickness of 200 to 400 m at the center and diameters more than 100 km. The lens-shaped thermostads have temperature of 19°C and a thermosteric anomaly of 300 to 320 clt^-1 when the Kuroshio takes a meandering path, and 17° and 260 to 280 clt^-1 when it takes a straight path.
   A detailed analysis of the water regions observed during two periods when the Kuroshio was meandering, which began in 1959 and 1975 respectively, shows that the warm water regions do not have a lens-shaped thermostad structure in the first years of the periods, but have it in the following years. There are some differences, however, between the two cases. The thermosteric anomalies in the thermostad gradually decrease with time in the former case and increase in the latter. The geographical location of the center of the warm water region off Shikoku is rather stationary in the former case and fluctuates with time in the latter.