The Effect of the Changing Arctic on Acoustic Propagation in the Beaufort Sea

It is well known that climatic changes are occurring in the Arctic ocean. In addition to the increasing heat content, the ice cover is decreasing, and the thermohaline stratification is adjusting to changes in the freshwater distribution. Less well known, but readily apparent, is that the acoustic propagation is also changing. A recent experiment, the Canada Basin Acoustic Propagation Experiment (CANAPE), sought to quantify some of these issues. Here we will briefly describe the experiment and comment on the observed changes. While the heat content is easily measured through the change in sound speed and the resulting change in the acoustic travel time, there are several other effects that are important. The acoustic attenuation will lessen as the ice cover gets thinner and smoother, the ambient noise will change with the changing ice fracture dynamics, the coherence time and bandwidth of the acoustic arrivals will decrease with the increase in internal wave energy caused by the increased exposure of the ocean surface to the wind, and, finally, the structure of the acoustic arrival pattern will change with the change in stratification. Some of these changes can be compared to historical measurements, but all of the CANAPE results provide an important baseline as the Arctic continues to evolve.