Modeling and measurement of relative intensity of acoustic arrivals within the beaufort duct

The Beaufort Duct, located at approximately 175 m depth in the Canada Basin, allows for long-range acoustic propagation from sources moored within the duct. As part of the Canada Basin Acoustic Propagation/Glider Experiment (CANAPE/CABAGE), LFM sweeps with frequencies around 250 Hz were transmitted by broadband moored sources and received by two Seagliders traversing between them. In addition to receiving acoustic data, these Seagliders measured temperature, pressure, and salinity, providing measurements of the sound speed profile throughout the CANAPE study region. These profiles were used as inputs for broadband acoustic parabolic equation predictions. Measured data receptions within the duct show intense peak arrivals prior to the final cutoff that are higher in relative intensity than predicted. The duct properties of the measured sound speed profiles are parameterized and acoustic predictions using actual profiles as well as idealized profiles are used to study the predictability of these intense peaks within the duct.