Environmental acoustic noise observations in Tethys Bay (Terra Nova Bay, Ross Sea, Antarctica)

Underwater acoustic measurements have been recently carried out in Tethys Bay (Ross Sea, Antarctica) during the XXIX Italian Antarctic Expedition to support acoustic propagation studies in the area and to investigate the environmental noise. Tethys Bay is a small deep cove close to the Antarctic Italian base Mario Zucchelli Station (Baia Terra Nova -74 degrees 42' S e 164 degrees 07' E) and covered with sea-ice for most of the year. During the period of the experiment (November 2013) the pack-ice had an almost constant thickness of about 2.2 m, so that the measurements were performed deploying the instruments into the sea from holes drilled through the pack ice. The holes were located along the bay axis at a distance of about 500 m each other. The sea depth was around 200 m except for the hole close to the coast, where the sea depth was only 25 m. An hydrophone RESON TC 4032 was located in the outermost hole, while the acoustic source, a transceiver transmitting FSK pulses at 11 kHz, was placed in sequence in the other three holes. Every time, the measurements were performed at 0, 20 and 45 m depth for each configuration. Furthermore during the experiment, sea temperature, salinity and currents, as well as the main meteorological parameters were continuously measured. The analysis here reported mainly focuses on the acquired acoustic passive data. The passive measurements evidenced that the signal was generally dominated by different sounds from seals, which was prevailing on the noise due to human activities.