Large-scale assessment of masking potential by underwater ship noise the North Sea

Abstract

The JOMOPANS project created one year of soundscape maps of the North Sea, based on ship information from the Automatic Identification System (AIS) and a ship source model. This assessed the potential impact of ship noise on the marine ecosystem through the masking of communication and other relevant acoustic signals. Specifically, the excess noise was quantified, which express the deterioration of the signal-to-noise ratio caused by the ship noise and hence the reduction in maximum communication range. The dominance of ship noise over natural sources was quantified as the percentage of time where excess was 20 dB or higher. A decrease in signal-to-noise ratio of 20 dB compared to a reference condition (ambient plus weather) without ships indicates a substantial decrease in communication range, and hence a substantial risk of impact on the ecosystem. Maps of excess and dominance in different frequency bands showed the largest ship contribution in the lowest frequency bands and in the most trafficked areas, with less affected areas in shallow waters, including the Dogger Bank. These maps, in combination with distribution maps of sensitive species, form the basis for the joint assessment of environmental status of the North Sea by the surrounding countries.