Reconstructing ocean properties from seismic data



Ocean temperature, density, and salinity change with depth on fine scales. Some scientists are beginning to use acoustic images to reconstruct these water column properties. In this technique, acoustic waves are generated in the ocean by an active seismic source such as an air gun array, and the reflected waves are recorded at surface. The recorded field is then carefully processed to obtain an acoustic image of the layer's reflectivity. The speed of sound and the amount of energy reflected and transmitted vary depending on the water's temperature and salinity, so these reflected acoustic waves indirectly contain information on the water properties. However, analyzing acoustic data to extract water column properties can be tricky. Kormann et al. show that a mathematical method known as full waveform inversion can be used to reconstruct high-resolution temperature and salinity profiles from simulated one-dimensional seismic ocean data. The work is a step toward making the method of using seismic data to retrieve water column properties more widely applicable. (Journal of Geophysical Research-Oceans, doi:10.1029/2011JC007216, 2011)