A SUBSURFACE COUNTERCURRENT ALONG THE EAST-COAST OF LUZON

A hydrographic section in the region east of Luzon was repeated 14 tim es during the period from 1986 to 1991. The data revealed the existenc e of a subsurface countercurrent located on the shoreward side of the Kuroshio with its upper boundary at about 500 m. The countercurrent, w hich should be called the Luzon Undercurrent (LUG), was only about 50 km wide, which is comparable to the baroclinic radius of deformation. Despite considerable variabilities both in velocity profile and intens ity, the LUC appears to be a permanent feature. Over the period of obs ervations, the maximum speed in the LUC calculated from the mean tempe rature and salinity by assuming geostrophy (relative to 2500 db) was 7 cm s(-1) at about 700 m and its mean geostrophic volume transport was 3.6 Sv (1 Sv = 10(6) m(3) s(-1)). About 28% of this transport was com posed of the low-salinity North Pacific Intermediate Water (NPIW) adve cted to the south along the coast of Luzon. (C) 1997 Elsevier Science Ltd.