Basin-scale internal wave tomography: Some first steps
John A. Colosi
Woods Hole Oceanographic Institution, Woods Hole, Massachussetts 02543 and The ATOC Group1
abstract: High frequency fluctuations in basin-scale acoustic transmissions offer intriguing possibilities for inferring average statistical characteristics of the ocean internal wave field. For the 1000-km SLICE89 experiment Monte-Carlo numerical simulations using the Garrett-Munk (GM) internal wave model were used to infer the average internal wave energy as a function of depth. This technique has the advantage of treating the forward problem very accurately, yet due to the computational intensity of the technique only variation of internal wave energy could be studied. To fully explore the parameter space of the GM model a simplified forward model based on a geometrical optics calculation of the phase structure function, D, is proposed which treats the acoustic observables of travel time variance, depth and time coherence. Vertical coherence is sensitive to the GM parameters of internal wave vertical wave number bandwidth and vertical wavenumber spectral slope. Temporal coherence is sensitive to the GM frequency spectrum slope. Horizontal coherence is not a good observable due to contributions from mesoscale eddies. This approach is being applied to the ATOC vertical line array data, and some preliminary results are shown. For acoustic energy which samples the upper ocean the GM model is not appropriate and a substitute model is needed.
1 Introduction
1The ATOC Group: A. B. Baggeroer (MIT), T.G.Birdsall (Univ. Michigan), C.Clark (Cornell Univ.), J.A.Colosi (WHOI), B.D.Cornuelle (SIO), D.Costa (Univ. CaJif. Santa Cruz), B.D.Dushaw (Univ. Washington), M.A.Dzieciuch (SIO), A.M.G.Forbes (CSIRO Hobart), B.M Howe, (Univ. Washington), D.Menemenlis (MIT). J.A.Mercer (Univ. Washington), K.Metzger (Univ. Michigan), W.Munk (SIO), R.C.Spindel (Univ. Washington), P.F.Worcester (SIO), and C.Wunsch (MIT).
