Propagation of seismic exploration noise in the Marginal Ice Zone Free

This paper presents data from ambient noise recordings in the Marginal Ice Zone (MIZ) in the Fram Strait (deep water) and Barents Sea (shallow water) with focus on noise due to seismic exploration activity. Data were recorded on fields of sonobuoys deployed from P-3C aircraft in June 2011 and May 2012, each covering a 100 km x 100 km area. Recordings from three bouys in each area, from open water to within the solid ice cover, are analyzed for low-frequency (10 Hz–1 kHz) noise levels, with broadband noise due to distant seismic exploration identified. Strong attenuation of this noise component with distance into the MIZ is observed in the shallow-water data, whereas noise levels decrease less with distance in the deep-water data despite under-ice conditions. Propagation loss is modeled using a raytrace model including under-ice reflection loss due to an elastic ice cover, with environment input from the TOPAZ coupled ocean-sea ice model and from satellite images. Properties of the noise field, modeling results, and model-data discrepancies will be discussed. [Data collected under the ACOBAR and WIFAR projects at NERSC.]