Observation of the abyssal current in the West Mariana Basin

Abstract

In order to investigate long-term variations of deep sea currents and temperature in the western North Pacific, a direct current measurement was made at 12.5°N, 137°E from July 1985 to July 1986. The current meter was moored at a depth of about 4,000 m (bottom depth 4,604 m) in the West Mariana Basin, very close to the deep water passage to the North Pacific Basin. Throughout the observed period, the current flows southward with an average speed of 0.8 cm sec−1. There are significant variations of both currents and temperature within the period of 60 days. For the shorter time scales, in addition to the tidal oscillations with one day and half day periods, there is a notable spectral peak of the current with a clockwise rotation at a period of 2.2 days, which is slightly shorter than the local inertial period of 2.3 days.