Oceanographic and underwater acoustics research : conducted during the period 1 May - 31 October 1965

Abstract

This progress report contains findings in 1) physical oceanography, 2) marine biology, 3) geology and geophysics, and 4) hydroacoustics. 1) Long-period internal waves are deduced from sound-velocity data between Bermuda and the Antilles . The region of the thermal front (usually found near 30°N) was thought on one occasion to be a generator of internal waves. 2) Midwater fishes were four times more abundant north of the front than south and midwater reverberation levels varied similarly. 3) Evidence obtained southeast of Charleston, S.C. shows that the continental shelf has been building out over the Blake Plateau. The gravity characteristics of many major rifts of the world reveal that as the width of the rift increases, the Bouguer anomalies become increasingly positive. 4) Observations support the hypothesis that diffraction effects are required to explain the sound propagation in convergence zones in the Mediterranean. A major engineering accomplishment was the installation and use of Sea Spider on the Blake Plateau. Sea Spider is a near motionless platform for scientific measurements in the deep ocean. The development of an automatic digital depth-reading system for use with echo sounders on ships were successfully completed, improvements in seismic profiling techniques were made, and special coherency studies of towed hydrophone array noise have progressed.