NARVAL2019: Ocean Acoustic Measurements in the Barents Sea Polar Front

In this paper, the authors describe a measurement campaign carried out in October 2019 in the Barents Sea by the CMRE (Center for Maritime Research and Experimentation), DGA Naval Systems (French Defense Procurement Agency), FFI (Norwegian Defence Research Establishment) and SHOM on the N/O Pourquoi Pas? Two acoustic pingers were moored north (Tx1) and south (Tx2) of the Polar Front, and transmitted sequences composed of Linear Frequency Modulation (LFM) and CW (Continuous Wave) waveforms between 1 and 14 kHz. The front was located precisely using the sea surface temperature sensors. Several acoustic receivers were deployed south of the front in a strongly range-dependent environment. A 32-hydrophone acoustic array was also towed across the Polar Front. In addition, oceanographic moorings were deployed: a 24-element thermistor chain (on the Tx2 mooring) and a WireWalker (north of the Tx2 mooring). They provide vertical temperature (and also salinity and density) measurements. Temperature fluctuations are various time scales were highlighted by the oceanographic recordings. In parallel, the influence of these environmental fluctuations on the received signals (on the various passive moorings) and ambient noise is shown by analyzing the measured channel impulse responses, phasors and transmission loss.