Acoustic-gravity waves in ocean and atmosphere generated by an underwater source

Abstract

Air-water interface becomes anomalously transparent, and the power flux in the wave transmitted into the air increases dramatically, when a compact sound source in water approaches the interface within a fraction of wavelength [O.A. Godin, Phys. Rev. Lett. 97, 164301 (2006)]. The anomalous transparency of the ocean-atmosphere interface has important implications for detection of underwater explosions and monitoring of compliance with the Comprehensive Nuclear Test Ban Treaty. At wave frequencies below 0.1 Hz, it becomes necessary to take gravity into account. Then fluid buoyancy and compressibility simultaneously serve as restoring forces, and mechanical perturbations in the water and in the air propagate as acoustic-gravity waves (AGW). It was previously shown [I. Fuks and O.A. Godin, Proc. OCEANS'11, MTS/IEEE, Kona, HI, Sept. 2011] that, in the case of a shallow source in an ocean of an infinite depth, a sharp peak in the power flux into air appears at frequencies close to a cutoff frequency of about 4mHz of a surface acoustic-gravity wave. In this paper, we extend these results to the ocean of a finite depth where the AGWs interact with an elastic bottom.