OC4331-Mesoscale Oceanography
Final Project Summary

Topic Area

LCDR Mike Cooper, USN

This project was a coincident project for physical oceanography requiring the use of real world data for acoustical purposes. It attempts to give a range dependant picture of sound propagation through a cold core eddy using ray theory.

The data used in this project was collected by the US Navy 4-7 February 1973 in the northeast Atlantic Ocean. The data consisted of 23 XBTs (depth, temperature) that provided a cross section of a cold core eddy with a diameter of approximately 350 km. Sound speeds were calculated using the XBT data and the Mackenzie sound speed profile. Since the XBTs only provided data down to 750m in an area where the average depth is 5000m, the sound speed profile was populated down to 2500m by a NAVO diagram of the same eddy and then interpolated to the bottom.

A source was then placed at 200m at the outside edge of the eddy and rays were then traced through the eddy using Aaron Young's source raytracing code adapted for use in this case. Sound speed profiles were updated every 40km as the rays progressed, and rays from a previous trace were launched on the next at approximately the same depth and angle. The same procedure was then run with a source at the center of the eddy at the same depth.

The basic finding in this project was that a cold core eddy acts as a lens that brings acoustic energy toward the surface as the deep sound channel rises in the eddy's center. While not directly depicted in this project, one could also conclude that acoustic energy would be focused toward the center on the horizontal since the horizontal sound speed profile also has a sound channel.

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