Inversion for bottom sound speed and bathymetry in a 3-D shallow-water Arctic environment

Abstract

Propagation modeling and matched-field processing (MFP) require a good knowledge of ocean-bottom properties on a grid of points covering the search region. These parameters can be difficult to measure in range-dependent Arctic shallow waters. An effective environmental model based on MFP inversion can be easier to obtain than extensive geophysical measurements and more effective for MFP if the same propagation model is used both for inversion and MFP. An even more effective model for MFP is obtained if inversion is carried out for several consecutive source positions. In developing MFP-based inversion for this scenario, recovering the bathymetry alone was investigated first, then both sound speed and bathymetry, for sources at a number of known ranges. After these successful inversions, inversion for recovering the unknown position of one source and the bathymetry was investigated. Both of these cases employed two-dimensional modeling but it is recognized that significant changes in the predicted field can occur when the third dimension is taken into account. Examples of seamounts and realistic shelf slope environments were modeled in three dimensions and the effect of inverting in two dimensions for bottom properties in the shelf slope case was investigated.