Impact of sound-speed structure on acoustic localization of autonomous underwater vehicles in the Canada Basin

In recent decades, the Canada Basin’s upper ocean structure has undergone changes with the intrusion of warmer Pacific Ocean waters and continued surface warming. These changes have direct implications for underwater acoustic propagation including the formation of a strong subsurface duct located around 180 m depth, referred to as the Beaufort duct. In summer 2016, a pentagonal array of tomography sources moored within the Beaufort duct over a region with a radius of approximately 150 km was deployed for a year to study acoustic propagation in this environment. In the summer of 2016 and 2017, two autonomous underwater vehicles (AUVs) profiled the upper 750 m of the water column. The AUVs, equipped with hydrophones, collected temperature and salinity profiles along with recordings of signals transmitted from the moored acoustic sources at ranges up to 530 km. In situ measurements are used to generate an empirical sound-speed perturbation field for acoustic predictions, used here to estimate acoustic ranging between moored sources and the AUV by matching received acoustic arrivals to the range-dependent acoustic predictions. Vehicle data are leveraged to Doppler correct ranging and to constrain localization solutions. Localization improvements and solutions within the tomographic array will be presented.