A direct measurement of near-bottom current on the continental slope off Omaezaki, central Japan.

Abstract

A direct measurement of the near-bottom current was made by a mooring system at (33°46.0'N, 137°37.3'E) off Omaezaki on the continental slope from December 21, 1980 to May 2, 1981. The observation level was 2200 m in depth and the bottom depth was 2300 m. The location is about 3 km east of the place where a deep sea pressure gage was installed by the Meteorological Research Institute (M. R. I.). The data obtained by the pressure gage are also analyzed. The current observed was generally west-southwestward along the isobaths of the continental slope in an opposite direction to the surface Kuroshio flow. For three times during the observed period, it turned its direction to the east-southeast with a down-slope component, lasting for 10 to 15 days. Temperature and pressure also varied, although not always, seemingly with the velocity changes. The time series of half-monthly averaged horizontal temperature distribution at 200 m depth (published by the Hydrographic Office, the Maritime Safety Agency of Japan) shows that the surface Kuroshio was generally flowing south of the observational point and also suggests that its axis possibly approached to or crossed the observation point northward with occurrences of small-scale meander of the axis which happened in the above three periods. It is suggested that there might be a dynamical link between the surface Kuroshio and the near-bottom flow far beneath the thermocline depth.