Study on the vertical migration characteristics of the acoustic scattering layer under the influence of internal waves in the northern South China Sea
Based on the Acoustic Doppler Current Profiler carried by deep-sea moorings,we investigated the diel vertical migration of the acoustic scattering layer and the impact of internal solitary waves on it in the northern South China Sea.The observational results reveal that the acoustic scattering layer,influenced by zooplankton,as-cends to shallower depth within approximately an hour after sunset,remains there throughout the night,then mi-grates to the deeper depth within about an hour before sunrise.The average migration velocities are 4.7 cm/s(up-ward)and 5.8 cm/s(downward).Additionally,internal solitary waves observed in the region induce a pair of down-ward and upward currents,with maximum vertical velocities exceeding 50 cm/s,leading to fluctuations of tens to hundreds of meters in the acoustic scattering layer.The acoustic backscattering strength of the ocean's upper layer reaches its maximum value at the troughs of internal solitary waves.Further research indicates that the daytime in-ternal solitary waves exhibit a stronger correlation between the vertical velocity and the depth-averaged backscatter-ing strength variation compared to the nighttime internal solitary waves.When the vertical velocities induced by both types of waves are equal,the depth-averaged backscattering strength variations during the day are typically greater than those at night.
Acoustic Doppler Current Profilerinternal solitary wavesacoustic scattering layerdiel vertical migrationSouth China Sea
万方数据
维普
