VERTICAL PROFILES OF HORIZONTAL OCEAN CURRENTS

Data collected from moored current meters at a single site (Site D) in the western North Atlantic are used to define vertical profiles of steady and time-dependent horizontal ocean currents. The mean velocity profile shows currents systematically flowing towards the west, with amplitude which decreases with depth. Time-dependent currents have a vertical profile of kinetic energy which is proportional to the vertical profile of Brunt-Väisälä frequency, N (z). Since the mean speed is dominated by time-dependent components, its profile is approximately proportional to N 1 2. At frequencies lower than 1 cycle per day, the time-dependent motion is not horizontally isotropic at all depths. In the surface layer, north-south (v) components have a larger variance than east-west (u) components; at mid-depths, the u-variance is greater; at great depths the variancesare approximately equal. At frequencies higher than one cycle per day, the motions are horizontally isotropic. The pattern of anisotropy may be due to the interaction between low-frequency processes and the nearby continental shelf. Eddy momentum fluxes have a profile which reverses sign at the approximate depth of the continental shelf. © 1969.