Modeled time variability of acoustic propagation through a Gulf Stream meander and eddies

Abstract

A numerical modeling study of the time variability of acoustic propagation through a Gulf Stream meander and eddies is presented. Both a cold-core (cyclonic) eddy and a warm-core (anticyclonic) eddy are included. Time periods of 2, 4, and 7 days; a frequency of 25 Hz; source and receiver depths of 150 m; and propagation out to 180 km are considered. Propagation conditions assumed an absorbing bottom and no azimuthal coupling of energy. Results indicate that variations in the locations and propagation loss levels of convergence zones (CZ) in 2 days can be significant. In the first CZ, the losses can change by more than 5 dB and shift in their pattern range location by as much as 10 km. Changes in the environment over a 2-day period can be such that perturbations to the acoustic field caused by the environment within the first CZ can be nullified by the environment between the first and second CZs. The differences between propagation with the eddies present and not present were also observed for ranges out to the first CZ. For a source located in the center of a cold-core eddy, the propagation loss in the CZ increased by 3 dB and the range decreased by about 5 km. With the source located within the eddy but off center, the loss showed little change in level but the range again decreased by about 5 km. For a source located in the center of a warm eddy, the propagation loss in the CZ increased by about 3 dB and the range increased by 7–10 km. With the source located off center, the loss showed little change in level and range location.