Modal analysis of broadband signal arrival on Beaufort shelf

Using previously reported temperature and salinity data collected over the past decade, time evolving sound speed profiles were constructed and used (Prog. Oceanography, 127, pp.1-20, 2014) as input to a parabolic equation model. Modeling of broadband acoustic signal propagation in the Arctic shelf-basin region during ice free sea surface season was reported recently (J. Acoust. Soc. Am. 136(4), Pt. 2, 2317, 2014). It was shown that when broadband acoustic signals propagate from deep water to shallow water, the modal dispersion is changed. The change is mostly affected by the water thermocline behavior in time and space and by source depth. The modal arrival structure can be influenced by a number of factors including the degree of Pacific warm water intrusion, upwelling of the warm saline Atlantic water into the cold surface layer, the range-dependence of the water layers over the shelf break, and the depth of the source. In this paper, we analyze the range-dependent propagation in terms of adiabatic and coupled mode regimes in order to explain the model results. [Work supported by ONR.]