Generation of Underwater Noise by the Rip Zone of a Large-Amplitude Internal Wave in the Ocean

The article discusses the results of measuring underwater noise generated by a large-amplitude solitary internal wave based on observations made near the Mascarene Ridge in the Indian Ocean. The measurements were taken from a ship drifting over large depths, equipped with a vertical string of hydrophones and equipment for recording internal waves. The parameters of the recorded 50 m internal wave and characteristics of the emitted underwater noise are given. Powerful orbital currents accompanying the internal wave form rips on the ocean surface: areas of chaotic, collapsing waves that increase the air bubble concentration in the near-surface layer and emit underwater noise. Analysis of the data showed that the passage of a rip caused by an internal wave over a hydrophone leads to a significant (up to 18 dB) increase in the level of underwater noise in the 5–15 kHz frequency range.