Basin-scale internal-wave tomography using a large-aperture vertical array

Abstract

Basin-scale acoustic transmissions which are received at a large-aperture vertical line array (VLA), like those deployed for the Acoustic Thermometry of Ocean Climate (ATOC) program, provide several acoustic fluctuation observables that can be used for internal-wave tomography. A single receiver provides observations of wavefront travel-time variance, pulse time spread, and temporal signal coherence. A VLA adds the observations of vertical wavefront coherence and modal time spread and time coherence. The combination of wavefront and modal observations provides tomographic vertical resolution of average internal-wave energies as a function of depth. In addition, vertical and temporal wavefront coherences are complementary observations, since spatial and temporal internal-wave variabilities are related through the dispersion relation. Also, vertical and temporal coherences help test the assumption of a separable internal-wave spectrum in terms of frequency and vertical wave number. First efforts to combine several of these acoustic fluctuation observations from the ATOC North Pacific VLAs in an internal-wave tomographic analysis will be presented. Directions for future research will be discussed.