Evidence for a North Pacific Deep Western Boundary Current

Four current meter moorings arrayed across the Japan Trench near 35 degrees N yielded 2 years of deep current velocities in the vicinity of the Kuroshio where it separates from the Japanese coast. One- and 2-year means are interpreted in the context of other observations, including concurrent hydrography, as well as the results of earlier investigations. Principal findings are as follows: the presence of a persistent, southward deep western boundary current (1-2 cm s(-1)) along the slope (2000-4000 m) inshore of the Japan Trench; a generally northward deep flow (similar to 4 cm s(-1)) over the trench, beneath the Kuroshio; and southward and eastward deep flows farther southeast of the Kuroshio separation. These deep, mean flows, particularly the one inshore of the Japan Trench, may be partly of thermohaline origin. Eddy-driven local recirculations and bottom intensification are also likely.