INFLUENCE OF ANTICYCLONIC EDDY SHEDDING FROM KUROSHIO LOOP ON SOUND PROPAGATION
Previous studies have shown that the Kuroshio often intrudes the South China Sea(SCS)in winter through a looping current,accompanied by shedding anticyclonic eddies.These shedding eddies bring high-temperature and high-salinity water from the Kuroshio into the SCS,affecting the spatial distribution of hydrological elements and acoustic fields.However,corresponding research about sound propagation caused by such eddies lacks.Utilizing altimeter satellite data and reanalysis data from 2009 to 2020,six anticyclonic eddies shedding from the Kuroshio were selected in the northeastern SCS during winter to study their hydrological and acoustic field structures,and to simulate their influence on sound propagation using the Bellhop Gaussian beam model.Results show that the average radius of the six shedding eddies was 110～135 km in 1 000～1 200 m depth with maximum geostrophic currents of 0.4～0.6 m/s.Warm water descends in the center of the eddy,causing positive temperature anomalies in the maximum of 2.5 ℃ in 100～250 m.The center of the eddy displays a three-core structure with negative-positive-negative salinity anomalies.The positive anomaly of the sound speed appears at 100～900 m in maximum of 8 m/s at 400 m depth.When sound waves go through the eddy,the position of convergence zone(CZ)would shift backward by 5～10 km,which is not affected by local topography.In contrast,when local terrain obstructs the reversal of sound lines,the position of the sound line in contact with the terrain would deflect,and the CZ may move forward or backward,with maximum backward shift of 29 km and the maximum forward shift of 23 km.Finally,when the depth of the sound source and receiver are both 300 m,the sound transmission loss caused by eddy would be increased by 10～15 dB in maximum from that of the eddy-free environment,and the reflection of terrain and the sea floor can also increase the transmission loss by 5～10 dB.This study shall have significant implications for deep-sea communication,remote exploration,and vessel reconnaissance and anti-reconnaissance in the northeastern SCS.
South China SeaKuroshio loopanticyclonic eddyconvergence zonetransmission loss
NETL
NSTL
万方数据
