Acoustic mode coupling by nonlinear internal wave packets in a shelfbreak front area
Duda, Timothy F.
MetadataShow full item record
KeywordContinental shelf; Internal waves; Mode coupling; Shallow water; Shelfbreak front; Solitary waves; Sound propagation
A computational case study of coupled-mode 400-Hz acoustic propagation over the distance 27 km on the continental shelf is presented. The mode coupling reported here is caused by lateral gradients of sound-speed within packets of nonlinear internal waves, often referred to as solitary wave packets. In a waveguide having unequal attenuation of modes, directional exchange of energy between low- and high-loss modes, via mode coupling, can become time dependent by the movement of waves and can cause temporally variable loss of acoustic energy into the bottom. Here, that bottom interaction effect is shown to be sensitive to stratification conditions, which determine waveguide properties and, in turn, determine modal attenuation coefficients. In particular, time-dependent energy loss due to the presence of moving internal wave packets is compared for waveguides with and without a frontal feature similar to that found at the shelfbreak south of New England. The mean and variability of acoustic energy level 27 km distant from a source are shown to be altered in a first order way by the presence of the frontal feature. The effects of the front are also shown to be functions of source depth.
Author Posting. © IEEE, 2004. This article is posted here by permission of IEEE for personal use, not for redistribution. The definitive version was published in IEEE Journal of Oceanic Engineering 29 (2004): 118-125, doi:10.1109/JOE.2003.822975.
Showing items related by title, author, creator and subject.
Enhanced acoustic mode coupling resulting from an internal solitary wave approaching the shelfbreak in the South China Sea Chiu, Linus Y. S.; Reeder, D. Benjamin; Chang, Yuan-Ying; Chen, Chi-Fang; Chiu, Ching-Sang; Lynch, James F. (Acoustical Society of America, 2013-03)Internal waves and bathymetric variation create time- and space-dependent alterations in the ocean acoustic waveguide, and cause subsequent coupling of acoustic energy between propagating normal modes. In this paper, the ...
A large-amplitude meander of the shelfbreak front during summer south of New England : observations from the Shelfbreak PRIMER experiment Gawarkiewicz, Glen G.; Brink, Kenneth H.; Bahr, Frank B.; Beardsley, Robert C.; Caruso, Michael J.; Lynch, James F.; Chiu, Ching-Sang (American Geophysical Union, 2004-03-04)In order to examine spatial and temporal variability of the shelfbreak front during peak stratification, repeated surveys using a towed undulating vehicle (SeaSoar) are used to describe the evolution of shelfbreak frontal ...
A compilation and description of hydrographic transects of the Mid-Atlantic Bight shelf-break front Lyne, Vincent D.; Csanady, Gabriel T. (Woods Hole Oceanographic Institution, 1984-04)Historical hydrographic transects of the Mid-Atlantic Bight shelf-break front are compiled by month and described in this report. Interannual variability of the meteorological forcing and slope water mass properties are ...