The Shallow Water Canada Basin Acoustic Propagation Experiment was conducted on the Chukchi Sea continental shelf from October 2016 to November 2017. The experimental goals were to access (1) long-range (basin-scale) and (2) short-range (shallow-water) spatial and temporal energy variation. This letter focuses on a 20-dB energy change of acoustic signals in the frequency band 700-1100?Hz from June to August 2017 occurring along two shallow-water tracks from a common source, correlated with the occurrence of an oceanographic event in the top 150-m water column due to a Pacific Water outflow from the Bering Sea and retreat of the Marginal Ice Zone.
The Pacific Arctic Region has experienced decadal changes in atmospheric conditions, seasonal sea-ice coverage, and thermohaline structure that have consequences for underwater sound propagation. To better understand Arctic acoustics, a set of experiments known as the deep-water Canada Basin acoustic propagation experiment and the shallow-water Canada Basin acoustic propagation experiment was conducted in the Canada Basin and on the Chukchi Shelf from summer 2016 to summer 2017. During the experiments, low-frequency signals from five tomographic sources located in the deep basin were recorded by an array of hydrophones located on the shelf. Over the course of the yearlong experiment, the surface conditions transitioned from completely open water to fully ice-covered. The propagation conditions in the deep basin were dominated by a subsurface duct; however, over the slope and shelf, the duct was seen to significantly weaken during the winter and spring. The combination of these surface and subsurface conditions led to changes in the received level of the sources that exceeded 60 dB and showed a distinct spacio-temporal dependence, which was correlated with the locations of the sources in the basin. This paper seeks to quantify the observed variability in the received signals through propagation modeling using spatially sparse environmental measurements.