Delving into the Two-Dimensional Structure of a Cold Eddy East of Taiwan and Its Impact on Acoustic Propagation

Abstract

A cold eddy was detected east of Taiwan. The two-dimensional (2-D) eddy structure for the cold eddy was constructed with Argo data. Results show that the eddy structure follows that of an ellipsoid, where the largest anomaly occurs near the center at almost 400 m depth. The horizontal diameter was 200 km, and the vertical diameter was 500 m. The 2-D sound speed profile feature model for the cold eddy based on the Argo profiles was established with the EOF method. With the feature model, acoustic propagation through both a stationary eddy and a moving eddy was investigated. Results suggest that the presence of the cold eddy could push the convergence zone up to 4 km closer to the source, where it acts as a convex mirror to focus the energy. The movement of the eddy would affect the transmission loss of the first group ray arrivals by about 1 dB, the time delay by about 0.01 s, and the receiver angle by about 0.8° when the source and the receiver were at 300 m depth and the receiver was located 300 km away from the source.