Deep flow on the continental slope off Omaezaki, in the northern part of the cold water region associated with the Kuroshio meander.

Abstract

A direct measurement of the deep flow was made at 33° 45.6′ N, 137° 35.8′ E on the continental slope off Omaezaki, Central Japan, for 136 days from December 1, 1982 to April 17, 1983. The mooring site is located in the northern part of the cold water region off the Tokai district with a bottom depth of 2200 m and a bottom slope of 4x10-2. Four current meters were deployed at 30 m (L1), 100 m (L2), 310 m (L3) and 1000 m (L4) above the bottom. Unfortunately, records of speed at L3 were not obtained, except for the first 16 days. The mean flow averaged over the whole period is southeastward at L1 (30 m above the bottom) and southward at L2 (100m). A velocity component normal to the large-scale isobaths is larger than a tangential component. This is different from the result obtained in a preceding observation (Ishizaki et al., 1983) made at almost the same position where the current at 100 m above the bottom was generally flowing to the west-southwest along the large-scale isobaths. The difference of the general flow directions is discussed. Temporal variations of the flow field are coherent between L1 (30 m) and L2 (100 m), and so are those of the temperature field among the lowest three levels. But the coherency between L4 (1000 m) and lower levels is not so apparent. Examination of vertical variation of the relative magnitude of the variances of the zonal and meridional velocity components indicates that the bottom control of the fluctuations is no longer effective at L4 (1000 m above the bottom). According to spectral calculations, more than half of the total fluctuation kinetic energy is contained in a frequency band (16.3-52 days in period), though the fluctuation energy levels are much different from each other.