Warm-core eddy effects on sound propagation in the South China sea.

• We used an automatic detection method to locate and track a warm mesoscale eddy from satellite data. • We deployed hydrophone and temperature-sensor arrays in the center and outside the eddy. • We recorded acoustic signals from explosive sources and chirped signals from a transceiver. • We combined the measured hydrological data to create a spatially and temporally dependent empirical model of the eddy. • We compared the simulations with and without an eddy to investigate the effects of the eddy on sound propagation. • We utilized the measured data to analyze the effects of the eddy on transmission losses to the two hydrographic arrays. • We employed recordings of the chirped signals to study the effects of the eddy on sound-energy fluctuations. The spatial and temporal redistribution of sound energy caused by a warm eddy was measured via a multiday experiment conducted in the South China Sea, utilizing two vertical line arrays, a mooring source, and some wide-band explosive sources. In the experiment area, a warm eddy was identified and tracked using an automatic detection method combined with the empirically reconstructed data. During the experimental period, the warm eddy diminished in size and kinetic energy until it vanished. The influence of the warm eddy on sound propagation during its lifespan is comprehensively analyzed and explained. The experimental acoustic results and simulations based on dynamic hydrographic data demonstrate that energy is redistributed both spatially and temporally due to the presence of the warm eddy. In comparison to the environment without an eddy, the first convergence zone disappears and the high-energy region appears in the typical position of the first shadow zone. The oscillating disturbance in energy is mainly affected by the fluctuation of sound speed caused by the warm eddy. [ABSTRACT FROM AUTHOR]