A Long Oceanographic Section from Kyushu, Japan to the Equator, 145°E in November 1989

Oceanographic observations using XBT and CTD system were carried out in the Western Tropical Pacific Ocean in November of 1989.A sharp thermocline whose core temperature of 20°C was found at depths between 100and 300m in the region from the equator to lat. 15°-00\u27N. From the region at lat.15°-00\u27N toward the north, the thermocline divided into an upper and a lower thermoclines.The Subtropical Mode Water was found at depths between 200 and 400m betweenthese thermoclines. The subsurface saline water with salinity more than 34.70‰, theNorth Pacific Tropical Water, exists in the thermocline depth and it extended as farsouth as about lat. 06°-30\u27N near the southern limit of the North Equatorial Current.The salinity minimum water with salinity lower than 34.40‰, the North Pacific IntermediateWater, extended from the north to south at depths between 500 and 800m. The transitionzone between the Western North Pacific Central Water and the Pacific Equatorial Waterbecomes shallower toward the equator from high latitude and decreased in thickness