Soundscape analysis in the Southern Ocean using elephant seals as acoustic glider of opportunity

The underwater ambient sound field contains quantifiable information about the physical and biological marine environment. Since 2011, we have been annually collecting underwater data over the migratory routes of bio-logged Southern Elephant Seal (SES). As done with classical underwater gliders, we extract from these data very high resolution (approximately 30 min/400 m) ocean ambient noise measurements. In this conference, we present an overall picture of the low-to-medium frequency (10–6000 Hz) ambient noise distribution and its variability in time and space at a regional scale within the Indian Ocean. We detail our methodology to extract robustly the measurements usually performed on ocean ambient noise, such as sound pressure level over different frequency bands and their statistical percentiles. Also, we present our first attempts of exploiting acoustic recordings from bio-logged SES to infer surface wind speed. Wind maps from the ASCAT satellite (IFREMER, France) were used to study correlation relations between surface wind speed and acoustic content (e.g., the ratio of sound pressure levels at 1 and 6 kHz). In complement, we test SVM and Neural Network methods to estimate the presence of different classes of winds (e.g., below and above 10 m/s) from underwater ocean noise.