Abstract
Little is known about the characteristics, distribution, and role of trapped air pockets present underneath the Arctic ice cover. Laboratory ultrasonic modeling results are presented demonstrating striking effects of small trapped air pockets underneath a floating plate on broadband pulsed flexural waves. The thickness of the trapped air pocket is small compared to a wavelength. The experimental studies were conducted on ice, Plexiglas, and glass plates floating on water. The air pockets increase the flexural wave velocity causing horizontal refraction and shadow zones in the plane of the floating plate. A variety of air pocket sizes and cluster configurations have been investigated. The presence of a shallow‐water pool on the top surface of the floating plate has a negligible effect on the flexural wave compared to an air pocket of the same dimensions located underneath the plate. A number of different phenomena occur causing the amplitude of the detected flexural wave to be attenuated or simplified. The new findings indicate that trapped air below the Arctic ice cover may play a significant role in Arctic acoustics. [Work sponsored by ONR.]
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