Influence of ocean surface scattering on shallow water geoacoustic inversion

In shallow water, acoustic waves interact with, and are influenced by, the ocean bottom and the time-varying ocean surface. Geoacoustic inversion methods estimate subbottom properties from remotely measured acoustic signals, but the techniques typically rely on flat sea surface reflection in the implemented forward models. In this talk, Bayesian inversion results from two acoustic datasets collected during the Seabed Characterization Experiment 2017 on the New England Mud Patch in the Middle Atlantic Bight are presented. Compressional sound speed, density, and attenuation in the subbottom layers are determined from maximum a posteriori estimation across an exhaustive parameter space. The first dataset was collected in a stormy sea state, where the nominal acoustic wavelength was 3 m and the significant sea surface height was 3.5 m. Acoustic measurements from the same source-receiver locations during a calm sea state comprise the second dataset. Subbottom properties estimated from each acoustic measurement are compared and the inadvertent physical relationship between surface scattering and inverted subbottom parameters is discussed. Finally, an incoherent inversion technique is introduced, producing agreement between subbottom parameter estimates from calm- and stormy-sea state acoustic measurements. Work supported by the Office of Naval Research.