Sound propagation from the Canadian Basin to the Chukchi shelf during Summer 2015

Abstract

During the summer of 2015 a pilot experiment for the Canadian Basin Acoustic Propagation Experiment (CANAPE) was conducted between deep Arctic basin and shallow Chukchi shelf. A vertical line array (VLA) was deployed on the shelf (72.336 N, 157.449 W) at a depth of 161 m from July 26 to August 13, 2015. Sound sources were deployed from R/V Sikuliaq at locations ranging from 131 to 375 km from the VLA. M-Sequences centered at 250 Hz (bandwidth of 62.5 Hz) were transmitted from each location. Discrete shipboard CTD data were conducted at each transmission location and continuous CTD data were recorded along the VLA. Water column data suggests a sound channel located vertically between Pacific and Atlantic waters near the depth of Arctic halocline layer. They also show upward shoaling of lower halocline waters onto the shelf. This upwelling over the continental slope moves the sound channel from offshore to onshore near the bottom. The axis of this sound duct is 100 m below the surface and is about 100 m thick. Received acoustic signals on the shelf increase rapidly in intensity at time scales that range from minutes to days. In this paper we show the acoustic variations are due to the variable sound speed profile. Signal intensity, noise, and temporal variability for geotime scale of minutes to hours are reported. Numerical simulations are conducted to investigate the associated acoustic effects in data. [Work supported by ONR 322OA.]