EMSO implementation and operation: DEVelopment of instrument module

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Using shipping noise for sound speed inversion in coastal areas

Publication . Santos, Ana Bela; Felisberto, Paulo; Jesus, Sergio

Passive sound speed estimation using radiated ship noise is an appealing approach for long-term ocean observation close to ship lanes. In this paper we analyze the noise recorded in two drifting vertical line arrays (VLAs) deployed 1 km apart, in Setubal's underwater canyon area off the west coast of Portugal during the RADAR' 07 sea trial. Automatic Information System (AIS) recordings for this period reveal a major tanker passing in the area, with its acoustic signature observed in the spectrogram as a characteristic striation time-frequency pattern. By cross correlation and beamforming of the received signals at the VLAs we obtain propagating paths traversing the hydrophones of both VLAs and respective travel times. Such information is used for sound speed estimation. We discuss the applicability of the method to track sound speed perturbations using historical sound speed profiles for the area obtained from CMEMS (COPERNICUS Marine Environment Monitoring Service). This work is a contribution for application in a passive ocean acoustics framework for the estimation of sound speed perturbations in the water column.

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