Observations of sound-speed fluctuations in the western Philippine Sea in the spring of 2009

TitleObservations of sound-speed fluctuations in the western Philippine Sea in the spring of 2009
Publication TypeJournal Article
Year of Publication2013
AuthorsColosi J.A, Van Uffelen L.J, Cornuelle BD, Dzieciuch M.A, Worcester P.F, Dushaw B.D, Ramp S.R
JournalJournal of the Acoustical Society of America
Volume134
Pagination3185-3200
Date Published2013/10
Type of ArticleArticle
ISBN Number0001-4966
Accession NumberWOS:000330119700069
Keywordsinternal wave spectrum; ocean mesoscale; propagation; tides
Abstract

As an aid to understanding long-range acoustic propagation in the Philippine Sea, statistical and phenomenological descriptions of sound-speed variations were developed. Two moorings of oceanographic sensors located in the western Philippine Sea in the spring of 2009 were used to track constant potential-density surfaces (isopycnals) and constant potential-temperature surfaces (isotherms) in the depth range 120-2000 m. The vertical displacements of these surfaces are used to estimate sound-speed fluctuations from internal waves, while temperature/salinity variability along isopycnals are used to estimate sound-speed fluctuations from intrusive structure often termed spice. Frequency spectra and vertical covariance functions are used to describe the space-time scales of the displacements and spiciness. Internal-wave contributions from diurnal and semi-diurnal internal tides and the diffuse internal-wave field [related to the Garrett-Munk (GM) spectrum] are found to dominate the sound-speed variability. Spice fluctuations are weak in comparison. The internal wave and spice frequency spectra have similar form in the upper ocean but are markedly different below 170-m depth. Diffuse internal-wave mode spectra show a form similar to the GM model, while internal-tide mode spectra scale as mode number to the minus two power. Spice decorrelates rapidly with depth, with a typical correlation scale of tens of meters.

DOI10.1121/1.4818784
Integrated Research Themes: 
Student Publication: 
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