Measured sound levels in ice-covered shallow water caused by seismic shooting on top of and below floating ice, reviewed for possible impacts on true seals

Abstract

Seismic surveying of the Arctic is important for several reasons, but also introduces some challenges. One is the concern that seismic data may affect the hearing of marine mammals living there, including true seals. We performed two seismic experiments on floating ice on Svalbard in the Norwegian Arctic in early March 2016 and late May 2017, just before and right after the ringed seal breeding period. We used a single airgun below ice and detonating cord on ice, measured sound levels in the water column, compared these with hearing capabilities of true seals found from previous studies, and observed the animal’s reactions when exposed to seismic waves in the field. We found that these actual seismic experiments have little potential to cause physical hearing damage, but temporary behavioural change may occur. We also observed a difference in measured sound levels, frequency content, and animal reactions, depending on the type of source used.