Influence of warm eddies on sound propagation in the Gulf of Mexico*

Abstract

Abstract An automatic detection method is employed to identify and track eddies in the Gulf of Mexico. The physical parameters of the eddies, such as lifespan, radius, and distribution position are first examined and used to determine the spatio–temporal evolution of a strong warm eddy separated from the Mexico current. Then, the influence of this strong warm eddy on sound propagation during its lifespan are comprehensively analyzed with the parabolic equation and explained by using the normal mode and ray theories. Additionally, the influence of mesoscale eddies on the redistribution of total depth-integrated energy among the normal modes in the deep water is also discussed. The variation of arrival angle is investigated to explain the spreading acoustic energy caused by eddies. Overall, the results show that warm eddies can change the propagation paths and cause the convergence zone to broaden and approach the sound source. Moreover, the warm eddy can disperse sound energy and cause the total depth-integrated energy to incline to a lower normal mode. Throughout the whole of these three periods (eddy generating, eddy maturing, and eddy terminating), the fluctuation in the transmission loss is up to 30 dB (depending on the relative location of eddy center to the source).