Modeling of seismic exploration noise reduction in the Marginal Ice Zone

Invited paper

Dag Tollefsen

Norwegian Defence Research Est. (FFI)

Tuesday 2 june, 2015, 15:00 - 15:20

0.8 Rome (118)

This paper presents measurements and modeling of ambient noise from recordings in the Marginal Ice Zone (MIZ) of the Fram Strait, with focus on noise due to distant seismic exploration. A P-3C aircraft mission flown in June 2011 deployed twenty sonobuoys in the MIZ from open water to within the ice cover. Data were analyzed for low-frequency (10 Hz - 1 kHz) noise levels, with noise attributed to distant seismic exploration identified. A reduction of these levels with distance into the MIZ has been observed and explained in terms of attenuation due to the ice cover. Propagation loss in the ocean-ice environment of the MIZ is modeled using a raytrace numerical model that includes range- dependent reflection loss due to an elastic ice cover. Environmental input to this modeling is taken from the TOPAZ4 ocean data assimilation system and from satellite images. Propagation loss, sea-ice reflection loss, and noise reduction dependence on sea-ice parameters and distribution is modeled and discussed.

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