Real - Time acoustic monitoring of ocean interiors using ocean acoustic tomography

The ocean acoustic tomography is a unique and powerful oceanographic tool that can give us a time-series of 3D snapshots of ocean interiors in nearly real time. JAMSTEC has realized such an ideal ocean acoustic tomography system combined with the Global Telecommunication Network (INMARSAT-C). A demonstration experiment was carried out in the western Pacific Basin in the summer of 1997. During this experiment, the time-series of 3D tomographic maps of temperature was successfully reconstructed every six hours. These maps showed the energetic meander of the Kuroshio Extension with high time resolution. Another tomographic observation experiment was conducted in the central equatorial Pacific Ocean from 1999 to 2000. The preliminary result showed the temperature and current fields changed strongly related to ENSO (La Nina). In the latter experiment, the processing time of measured data was greatly reduced and a tomographic snapshot was reconstructed in nearly real-time. Our aim to monitor the ocean inferiors in real-time is almost