The speed-dependent underwater source level of a snowmobile traveling on sea ice.

Snowmobiles are a source of underwater anthropogenic sound in northern coastal environments. A field experiment to determine the acoustic properties and underwater radiated sound level of a snowmobile was conceived, designed, and executed in collaboration with the Nunatsiavut Government and the communities of Hopedale and Postville (Canada). Hydrophones were placed below the sea ice and a snowmobile was driven past the sensors at different velocities (30-100 km/h). The experiment was conducted in Caraquet, New Brunswick; Hopedale, Newfoundland, and Labrador; and Postville, NL, with improvements added to the procedure following each iteration. Snowmobile make and model, sea ice thickness, and ocean temperature and salinity were recorded at each location. Snow and ice conditions were qualitatively recorded. The contact between the skis and track with the snow and ice are the primary sources of underwater sound for a snowmobile in motion. Both of these mechanisms generate sound at the point of contact, which radiates through the ice into the seawater. An equivalent source level for a monopole placed at the ice-water interface was calculated over the band of 80-400 Hz to be between 134-145 dB re 1 μPa2m2 and increased with snowmobile speed.