2aAO7. Observations, characterizations, and acoustic effects of nonlinear internal waves on the Mid-Atlantic Bight continental shelf.

Session: Tuesday Morning, December 3

Time: 9:35

Author: Ching-Sang Chiu
Location: Code OC/Ci, Dept. of Oceanogr., Naval Postgrad. School, Monterey, CA 93943
Author: James F. Lynch
Location: Woods Hole Oceanograph. Inst., Woods Hole, MA
Author: Marshall Orr
Location: Naval Res. Labs., Washington, DC
Author: Donald W. Taube
Location: Naval Postgrad. School, Monterey, CA 93943
Author: Seng L. Ng
Location: Naval Postgrad. School, Monterey, CA 93943


During the summer of 1995, a multi-institutional field study called Shallow Water Acoustics in a Random Medium (SWARM) was conducted in the Mid-Atlantic Bight continental shelf region off the coast of New Jersey. Environmental and acoustic sensors were deployed as part of SWARM to measure and characterize the nonlinear internal waves and their impact on the spatial and temporal coherence of the acoustic transmissions. As part of the environmental monitoring network, two bottom-moored, upward-looking acoustic Doppler current profilers (ADCPs) were deployed. An oceanographic, modal, time-series analysis of the ADCP data reveals that: large-amplitude, nonlinear, internal wave packets were generated at multiple sites near the shelfbreak; the generation mechanism was consistent with the lee-wave hypothesis of generation; the propagation characteristics were in good agreement with nonlinear soliton theory; and the power spectral density was spatially varying and changed markedly during the passage of these nonlinear waves. Based on these observations, a canonical model of the induced sound-speed perturbations was developed. Using a coupled normal-mode propagation model, the temporal and vertical structures of the sound field were subsequently calculated for comparison to data obtained by a vertical line array. [Work supported by ONR.]

ASA 132nd meeting - Hawaii, December 1996