A case study for analyzing future scenarios of underwater noise generated by shipping traffic in the Canadian Arctic

Abstract

The decrease of sea ice in the Canadian Arctic got the attention of the shipping community as this fact, associated with economic and social factors such as growing community re-supply needs and adventure tourism, are resulting in a considerable increase of shipping traffic levels and thus underwater radiated noise. Low frequency noise generated by propellers and ship machinery overlaps with sound frequencies used by mammals to communicate, reproduce and navigate, posing risks to the marine fauna.

Therefore, this study proposes a process to estimate the sound level generated by three kinds of vessels (cruise, cargo and tanker ships) in the regions of Lancaster Sound and Baffin Bay, including estimating future ship traffic volumes in 2040. The resulting sound field would depend on ship traffic levels, vessel sizes, changes to ship design which may affect generated noise, operating parameters (particularly vessel speed), and water conditions which can affect sound propagation. This study considers all of these factors.

Vessel traffic throughout the Canadian Arctic has tripled over the past 20 years and is not expected to decline. Through historical data analysis, derived from five years of ship traffic data, regression analysis was used to examine the relationship that the population and gross domestic product of the territory of Nunavut have with the shipping traffic levels and expert opinion was used to estimate most likely values of the noise generated by future fleets. Received Level (RL) and Sound Exposure Levels (SEL) were calculated through Monte-Carlo simulation and results were produced as a probabilistic distribution function (PDF) to understand the potential cumulative shipping noise that adjacent whales may be exposed to.

The results of this study showed higher sound levels expected for the areas, reaching levels that could result in temporary hearing loss, according to thresholds set out by the National Oceanic and Atmospheric Administration. The results also indicate which of the multiple factors considered would have the greatest effect in changing overall noise levels in the future. Modelling the escalation of underwater noise can help for risk mitigation planning and the advancement of spatial and vessel management tools for more sustainable shipping in the Canadian Arctic.