A numerical model for ocean ultra-low frequency noise: Wave-generated acoustic-gravity and Rayleigh modes

Type Article
Date 2013-10
Language English
Author(s) Ardhuin FabriceORCID1, Lavanant Thibaut1, Obrebski Mathias1, Marie Louis2, Royer Jean-YvesORCID3, D'Eu Jean-Francois3, Howe Bruce M.4, Lukas Roger4, Aucan Jerome5
Affiliation(s) 1 : IFREMER, Lab Oceanog Spatiale, Plouzane, France.
2 : UBO, IFREMER, Lab Phys Oceans, CNRS,IRD,UMR6523, Plouzane, France.
3 : CNRS, Domaines Ocean, Plouzane, France.
4 : Univ Hawaii Manoa, Sch Ocean & Earth Sci & Technol, Honolulu, HI USA.
5 : Lab Etud Geophys & Oceanog Spatiale, Toulouse, France.
Source Journal Of The Acoustical Society Of America (0001-4966) (Acoustical Soc Amer Amer Inst Physics), 2013-10 , Vol. 134 , N. 4 , P. 3242-3259
DOI 10.1121/1.4818840
WOS© Times Cited 23
Abstract The generation of ultra-low frequency acoustic noise (0.1 to 1 Hz) by the nonlinear interaction of ocean surface gravity waves is well established. More controversial are the quantitative theories that attempt to predict the recorded noise levels and their variability. Here a single theoretical framework is used to predict the noise level associated with propagating pseudo-Rayleigh modes and evanescent acoustic-gravity modes. The latter are dominant only within 200 m from the sea surface, in shallow or deep water. At depths larger than 500 m, the comparison of a numerical noise model with hydrophone records from two open-ocean sites near Hawaii and the Kerguelen islands reveal: (a) Deep ocean acoustic noise at frequencies 0.1 to 1 Hz is consistent with the Rayleigh wave theory, in which the presence of the ocean bottom amplifies the noise by 10 to 20 dB; (b) in agreement with previous results, the local maxima in the noise spectrum support the theoretical prediction for the vertical structure of acoustic modes; and (c) noise level and variability are well predicted for frequencies up to 0.4 Hz. Above 0.6 Hz, the model results are less accurate, probably due to the poor estimation of the directional properties of wind-waves with frequencies higher than 0.3 Hz.
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Ardhuin Fabrice, Lavanant Thibaut, Obrebski Mathias, Marie Louis, Royer Jean-Yves, D'Eu Jean-Francois, Howe Bruce M., Lukas Roger, Aucan Jerome (2013). A numerical model for ocean ultra-low frequency noise: Wave-generated acoustic-gravity and Rayleigh modes. Journal Of The Acoustical Society Of America, 134(4), 3242-3259. Publisher's official version : https://doi.org/10.1121/1.4818840 , Open Access version : https://archimer.ifremer.fr/doc/00176/28748/