Conference_programme: 27.2 - Underwater Noise II: Sources and remote sensing of the marine environment

Lecture: Polar coastal soundscapes: tracking of drifting icebergs with a compact sensor array

Author(s): Lossent Julie, Gervaise Cédric, Gay Michel, Chauvaud Laurent, Jolivet Aurélie, Mars Jérôme, Amice Erwan, Chauvaud Sylvain, Olivier Frédéric, Sejr Mikael

Summary:
Polar areas show fast changes linked to global warming. The reduction of the ice pack and the melting of the ice sheet modify the conditions of living of marine fauna. We propose the simultaneous monitoring of the ice and benthic fauna using passive acoustics. Thanks to a compact sensor array of 4 hydrophones (2m*2m*2m), we detected, localized and mapped in three dimensions ({azimuth, elevation} or {x, y, z}) the biophonic and geophonic contributions made up of short and broadband transient sounds. Tridimensional maps of benthic biophony and ice geophony of Antarctic and Arctic 3 days-long recording sessions (2015, 2016) are built and analyzed over a surface of the order of 1 km2. Benthic invertebrates emit high energetic pulses with peak frequencies ranging from 1.5 to 60 kHz, most of them below 15 kHz. Geophony is structured into two parts: 1) punctual distant loud sounds, which account for "major" events such as detachments of icebergs during the calving of a glacier or sea ice cracks and 2) Broadband Transient Sounds (BTS). These BTS have two main origins. The ice sheet, located several kilometers or tens of kilometers away, creates a stable spatial distribution of low energetic pulses (representing the majority of pulses in the soundscape) modulated by the temporal variability. The movements of isolated icebergs or pack ice produce localized acoustic events identifiable by the high sound levels and the stable peak frequencies of the emitted pulses. The drifting icebergs were tracked over time and in a 7000m² area. The source level of these icebergs was estimated at 148,6 +/- 4,6 dB re 1µPa at 1m that represent a propagation range of 300m.

Corresponding author

Name: Ms Julie Lossent

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Country: France