Abstract:

This paper describes an inversion of ambient noise fields measured in the Arctic in an attempt to determine the spatial distribution of ice-ridge building events in the polar ice pack. To this end, a matched-field algorithm is developed to localize multiple broadband sources in a range- and azimuth-dependent environment where the bathymetry is poorly known. Both the source locations and unknown bathymetric parameters are included as variables in a simulated annealing inversion that searches for the best match between the measured and modeled fields. A number of aspects of this problem are considered in a synthetic study including the importance of simultaneous inversion, the effect of bathymetry errors, and the problem of determining the number of sources present. The inversion accurately localizes multiple synthetic sources. The method is also applied to a set of ambient noise measurements recorded in the Lincoln Sea in the Canadian high Arctic. The results indicate that a small number of ice-ridging events is sufficient to accurately model the measured fields. Estimates of the number of sources and source bearings are unambiguous; however, source ranges could not be estimated unambiguously.