Measurements of deep water movements with instrumented neutrally buoyant floats

Abstract

The movements of deep water at 27°56′N, 55°22′W, were studied by means of instrumented neutrally buoyant floats. Five such floats were dropped together. They settled at slightly different depths near the 2300-meter level. The center of this cluster moved in a curved path to the southeast at an average speed of 2 cm sec−1. One of the floats, 140 meters deeper than a second one, moved relative to the second float in an almost circular path approximately 2 km in diameter and with an orbital velocity of 8.2 cm sec−1 and period of 25.2 hours. Variations in temperature amounting to ±0.02°C took place at a float. The variations in depth, approximately 4 m, rms, implied vertical water movements of 14 m rms. Spectrums were obtained for the variations of depth, temperature, and separation between two floats with time. The vertical temperature profile of the water was obtained from the temperature and depth data transmitted by a float which was made heavy enough to sink slowly to the bottom. The temperature gradient found was not monotonic with depth even near the bottom. An analysis of the characteristics of internal waves suggests that such waves caused most of the water movements.