Slice89: A Single Slice Tomography Experiment

Acoustic travel times in the ocean are sensitive both to the mean sound speed field and to high-wavenumber ocean features with wavelengths corresponding to ray loop “wavelengths” and their harmonics (70 km and smaller). The quasi-sinusoidal rays can be thought of as taking a partial Fourier transform of the sound speed field (Cornuelle and Howe, 1987). The SLICE89 experiment was conducted in the northeast Pacific during summer 1989 to determine how well high-wavenumber information can be resolved in practice. A broadband acoustic source near the sound channel axis transmitted to hydrophones 1000 km away. Preliminary travel time data from multiple receivers distributed through the water column are combined to construct time fronts. The measured time fronts are compared with predictions based on the sound speed field as calculated from CTD and XBT data taken concurrently. Although inversions of the measured travel time data are not yet complete, simulations are presented to show the horizontal resolution that can be attained.