Near‐bottom currents measured in 4 kilometers depth off the Baja California Coast

Measurement of water currents 3 meters above the bottom in 3700 to 4300 meters depth from 300 to 800 km west of the northern Baja California coast shows a net transport of about 2.2 cm sec−1 toward the southeast and semidiurnal fluctuations of an rms amplitude of about 1.7 cm sec−1, rotating counterclockwise. Both motions are generally coherent over dimensions of the order of 200 or more km, and the phase of the fluctuations is also coherent with the tides at La Jolla, California, 400 to 800 km away. The fluctuating motion may be ascribed principally to surface tides, since random motions and incoherent internal tides contribute not more than one-half of the observed velocities. The observed tidal fluctuations involve a calculated unit-area power dissipation several orders of magnitude less than the oceanic mean.