Convergence Zone Propagation in the North-East Pacific

Abstract

Oceanographic factors cause the sound velocity minimum in the Gulf of Alaska and the neighboring portions of the North-East Pacific to occur at a much shallower depth than in more southerly waters. As a result it is fairly easy to make experimental measurements with hydrophones at depths near the vertex. Measurements using pulsed CW signals of sound level against range have been made at several locations with arrays including hydrophones at various depths. These measurements have been compared with predictions based on ray tracing assuming a series of layers each with constant velocity gradient. Use of the Kuwahara sound-velocity relationship predicts too short a range for the convergence. Work is in progress to utilize predictions based on the work of Wilson. The pulse-to-pulse amplitude fluctuation is small, indicating at least short-term stability in the acoustic path without much effect from surface or internal waves.