Acoustic signals received on buoyancy gliders in the Beaufort Sea

Abstract

The buoyancy glider is a quiet and persistent underwater acoustic receiving platform. Traveling in a sawtooth pattern, buoyancy gliders equipped with acoustic recorders can sample acoustic transmissions at many ranges and depths with respect to moored acoustic sources transmitting on a timed schedule. In the Beaufort Sea, six broadband acoustic tomography sources consecutively transmitted 135-s linear frequency modulated (LFM) swept-frequency signals centered near 250 Hz every 4 h. These signals were received by two Seagliders at ranges up to 500 km and depths between the surface and 800 m in the summer of 2017. Sources were moored within the Beaufort Duct, a sound-speed minimum characteristic of the region, at a depth of approximately 180 m. Due to the presence of this duct, many acoustic paths are focused within a relatively narrow depth span, resulting in a complicated arrival structure. Pulse-compressed acoustic signals received on the gliders are interpreted in the context of broadband acoustic arrival predictions. The individual snapshots of acoustic arrival structure that make up this unique dataset offer insight into the acoustic travel-time arrival structure as it evolves with range from a transmitting source.