Tomographic measurements of barotropic motions

Abstract

In 1983, continuous acoustic transmissions centered at 133 Hz and with a resolution of 60 ms were transmitted for five days from Oahu to the coast of Northern California (4000 km range). A maximum likelihood estimate of the change in acoustic travel time (based on phase) between received pulses is used to estimate barotropic fluctilations. Analysis of the resulting time series reveals resonant oscillations at nontidal frequencies in the Northeast Pacific. Some of the periods of the resonant oscillations are consistent with theory (Platzman, Curtis, Hansen, and Slater, 1981). A Wiener filter is formulated for estimating the barotropic tides from a basin scale tomographic array. Error analyses indicate an ability to estimate barotropic currents and surface displacements with errors less than 0.01 cm/s and 1 cm, respectively, over a large portion of the Northeast Pacific.