Acoustic out-of-plane scattering off landslide bathymetry using an autonomous underwater vehicle at the New England shelfbreak

Abstract

During the New England shelf break acoustics (NESBA) experiment in May 2021, an acoustic autonomous underwater vehicle (AUV) was deployed to investigate bathymetric scattering processes at the shelfbreak. The AUV, consisting of a modified REMUS 600 vehicle with an onboard 2.5–4.5 kHz transducer and towed hydrophone array, passed over a submarine landslide site characterized by a steep escarpment and rocky debris field. AUV source signals received on nearby mooring hydrophones showed a complex interference pattern of overlapping bottom returns caused by this intricate bathymetry. A series of computational propagation models were tested to understand the bottom return data and scattering physics of this site. Ray tracing as well as 2-D and 3-D broadband parabolic equation (PE) models were used to simulate acoustic arrivals, which were then compared to the data for validation. While all models reproduced the primary features observed in the data, features attributed to out-of-plane 3-D scattering effects were best reproduced with the 3-D broadband PE model. [Work supported by the Office of Naval Research.]