Bubble effects on upper ocean acoustics under wind-driven seas

Abstract

Dense clouds of bubbles—ranging in scale from 10s of micrometers to cm—are generated by breaking waves on wind-driven seas. Wave-induced bubbles increase ocean albedo and play an important role in air-sea exchange processes by enhancing the transfer of gases and generating sea spray aerosol. Because bubbles both scatter sound efficiently and generate pulses of sound on formation, they create important acoustical effects, including the generation of ambient sound, the attenuation and scattering of sound forward scattered from the sea surface, and enhanced surface backscattering at low grazing angles. Examples of these effects will be illustrated along with the treatment of a bubble cloud acoustical scattering regime characterized by low absorption but high phase distortion relevant to high-frequency, coherent acoustic communications. [Work supported by ONR Ocean Acoustics.]