Statistics of acoustic intensity fluctuations caused by non-linear internal waves of elevation in shallow water in the South China Sea.

Abstract

In April 2007, a 6-day long field experiment was conducted to measure internal waves and their acoustic effects at the edge of the continental shelf in the Northern South China Sea. Very large internal solitary waves of depression originating in the Luzon Strait generate trains of internal elevation waves as they encounter a subaqueous bluff at the shelf edge in 120-m water depth. The acoustic transect, from the moored acoustic source transmitting 400-Hz m-sequences to two vertical line arrays moored at 3- and 6-km ranges, was oriented roughly parallel to the crests of the passing internal elevation waves, so as to observe the strong horizontal refraction effects which occur under such conditions. Statistics of and correlations between the internal wave characteristics and their associated effects on acoustic propagation are presented. [Work supported by ONR.]