Receptions of Kauai Beacon transmissions by ocean observatories initiative hydrophonesa)

The Kauai Beacon (KB), which began regular transmissions in March 2023, presents an opportunity to leverage existing hydrophones for ocean basin acoustic observations. This study examines KB receptions at the Ocean Observatories Initiative (OOI) hydrophones. Positive receptions are reported at eight of the 11 hydrophone locations. Observed arrivals are compared to simulated acoustic propagation. Analysis reveals that four OOI hydrophone locations demonstrate consistent arrivals suitable for tracking acoustic travel-time fluctuations, making them promising candidates for traditional ocean acoustic tomography applications. Analysis of the complex envelope statistics shows that acoustic simulation with internal waves effectively reproduces the observed arrivals at most locations. A notable exception is the Oregon Offshore hydrophone, bottom-mounted on the continental slope, where measured receptions lack the anticipated increase in acoustic energy associated with lowest mode order arrivals. This suggests enhanced mode coupling beyond standard Garrett-Munk energy internal wave energy predictions. This work demonstrates the potential for utilizing existing passive acoustic monitoring infrastructure for ocean basin observations and provides insights into single-hydrophone, long-range acoustic propagation that can inform future developments in acoustically observing ocean basins.