title: The influence of sea ice, wind speed and marine mammals on Southern Ocean ambient sound.
abstract: This paper describes the natural variability of ambient sound in the Southern Ocean, an acoustically pristine marine mammal habitat. Over a 3-year period, two autonomous recorders were moored along the Greenwich meridian to collect underwater passive acoustic data. Ambient sound levels were strongly affected by the annual variation of the sea-ice cover, which decouples local wind speed and sound levels during austral winter. With increasing sea-ice concentration, area and thickness, sound levels decreased while the contribution of distant sources increased. Marine mammal sounds formed a substantial part of the overall acoustic environment, comprising calls produced by Antarctic blue whales (Balaenoptera musculus intermedia), fin whales (Balaenoptera physalus), Antarctic minke whales (Balaenoptera bonaerensis) and leopard seals (Hydrurga leptonyx). The combined sound energy of a group or population vocalizing during extended periods contributed species-specific peaks to the ambient sound spectra. The temporal and spatial variation in the contribution of marine mammals to ambient sound suggests annual patterns in migration and behaviour. The Antarctic blue and fin whale contributions were loudest in austral autumn, whereas the Antarctic minke whale contribution was loudest during austral winter and repeatedly showed a diel pattern that coincided with the diel vertical migration of zooplankton.
authors.affiliation: Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany; Institute of Marine Research, Bergen, Norway.
authors.forename: Sebastian
authors.identifier: 0000-0002-2680-9794
authors.initials: S
authors.lastname: Menze
authors.affiliation: Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany; Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution, Woods Hole, MA, USA; Biophysics Group, Department of Physics, University of Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Daniel P
authors.identifier: 0000-0001-9429-4350
authors.initials: DP
authors.lastname: Zitterbart
authors.affiliation: Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research , Bremerhaven , Germany.
authors.forename: Ilse
authors.initials: I
authors.lastname: van Opzeeland
authors.affiliation: Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research , Bremerhaven , Germany.
authors.forename: Olaf
authors.initials: O
authors.lastname: Boebel
keywords: Antarctic marine mammals; Southern Ocean; ocean ambient noise; ocean ambient sound; passive acoustic monitoring; sea ice