Measuring phase difference to sense small-scale ocean sound-speed structure

Observations from a broadband acoustic experiment in deep water probe the temporal behavior of mid-frequency propagation through sound-speed fine structure advected by internal waves. The measured phases of two arrivals with similar propagation paths at 1.8 km range are sampled every 63.5 ms for 30 min. Simultaneous measurements of ocean fine structure near the propagation are used to model the changing arrival phase. The phase difference between arrivals is analyzed to understand changes in the underwater acoustic channel at the meter scale. A comparison between modeled and observed phase difference highlights an internal wave driven signal in the acoustic observations.