Oceanic current and temperature gradients at 12°N, 27°W

Abstract

Temperatures and pressures were measured at neutrally buoyant floats as they sank and while they remained at equilibrium depths for over 4 days at the location 12°N, 27°W in the Atlantic Ocean near Cape Verde. Two clusters of five floats each were used. One hovered at depths near 3700 meters, and the other remained near 4500 meters. Temperatures, temperature gradients, and sinking velocities were then determined as a function of depth. The separation between a particular float and any other float of its cluster was also found as a function of time and depth, so that information was obtained on the extent of the shear of the horizontal current with respect to the vertical direction. The measurements also showed the extent of the vertical and horizontal movement in deep water while the floats hovered. The mean flow over a period of 4 days at a depth of 3800 meters was 2 cm sec−1 in an ESE direction and that at 4680 meters was 1 cm sec−1 in the same direction. There was an additional inertia current of approximately 3 cm sec−1, which varied appreciably with depth. Fluctuations in the average inertia current compared in magnitude with the current itself. There were also vertical movements of the water amounting to approximately 20 meters rms at periods favoring the Brunt-Vaisala and lower frequencies. The pertinence of these results to the stability and rate of diffusion in deep water is discussed.