IUGG 2003 Abstract

P03 The Role of Tides, Mesoscale Processes, and Bottom Topography in Energy Transfer and Mixing Tuesday, July 1 AM Location: Site B, Room 19 Presiding Chair:S. Thorpe

TIME [ 1200 ] [ P03/01A/B19-008 ]

OCEAN-ACOUSTIC STUDIES OF SOLITARY WAVES OF DEPRESSION AND ELEVATION

Alex C. WARN-VARNAS(US Naval Research Laboratory, Stennis Space Center, MS 39529, USA)

Stan CHIN-BING(US Naval Research Laboratory, Stennis Space Center, MS 39529, USA) David KING ( US Naval Research Laboratory, Stennis Space Center, MS 39529, USA ) Jim HAWKINS ( Planning Systems Inc.,Slidell, LA 70458, USA ) Kevin LAMB ( University of Waterloo, Waterloo, Ontario, Canada N2L 3G1. ) Jim LYNCH ( Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA. )

We are performing internal solitary wave studies in the Strait of Messina, Gulf of Gioia, Yellow Sea, Primer, and ASIAEX areas. In these areas there are on shelf and off shelf propagating internal solitary waves that are generated by tidal flow over topographic changes in the sea floor and shelf break. In the course of these studies, two different types of internal solitary waves have come to light: the well-observed solitary waves of depression that peak in the pycnocline near the surface and propagate away from the shore (off the shelf), and the less noticed solitary waves of elevation that are formed around the shelf break and propagated toward shore near the bottom of the shelf. Illustration of the two types of solitary waves are shown from Yellow Sea and winter Primer simulations. The oceanographic simulations are performed with the Lamb(1994) model. The model is nonhydrostatic and is formulated in 2.5 dimensions using terrain following coordinates. The Lamb model is initialized from data, tuned to observations, and is forced with a prescribed semidiurnal tidal velocity. The structure of the simulated solitary wave packets compare favorably with the measured data, both in period and amplitude. Acoustical field calculations are performed with a parabolic equation acoustical model along the path of solitary wave packet propagation by coupling with the sound speed derived from the oceanographic simulations. In the Yellow Sea it is shown that solitary wave packets of depression propagating away from shore. Acoustical intensity predictions with the parabolic equation model indicate that anomalous loses in acoustical energy occur over the spatial and temporal bands at certain frequencies. The acoustical modes are calculated and the loss mechanisms are analyzed. In the winter Primer simulations it is shown that solitary waves of elevation propagate onto the shelf. They originate from internal bores that form on the shelf break and move onto the shelf as the direction of the semidiurnal tide reverses. The solitary waves of elevation are pronounced near the bottom of the shelf and their effects extend to the bottom of the winter mixed layer that is, 50 m to a 100 m deep. The propagation occurs under a deep winter mixed layer. Interestingly for this case, no off the shelf solitary wave trains form nor propagate away from shore, in agreement with data. This is a first time ever confirmation of this winter Primer observed phenomena through modeling simulations. Results will be presented and discussed that illustrate the similarities and differences between the acoustic effects produced by the near-surface and near-bottom solitary wave packets. [Work supported by ONR/NRL.]