 Prof. Anatoliy Nikolayevich Ivakin, University of Washington
Personal profile: Senior Principal Physicist, Applied Physics Laboratory, University of Washington, Seattle, USA
Email: aniv@uw.edu, Phone: 206-616-4808, www.apl.uw.edu/ani
Anatoliy Ivakin’s research interests include wave propagation and scattering in continuous and discrete media with rough interfaces and volume heterogeneity, theoretical and numerical modeling of random processes and fields, signal processing and inversion techniques, environmental acoustics and applications to underwater reverberation and remote sensing, seabed and sea ice characterization, marine ecology, and environmental monitoring. Dr. Ivakin is a Fellow of the Acoustical Society of America.
Presentation title: Under-ice acoustic propagation and reverberation in Arctic environments
Abstract: In this presentation, a modeling approach and a model-based analysis of sound transmission in a deep ice-covered Arctic ocean recorded during the Ice Experiment 2014 (ICEX14) is presented and discussed. A source of opportunity transmitted mid-frequency (3500 Hz) 5 second duration continuous wave pulses. The source and receiver were omnidirectional, located under ice at a 30 m depth at a 719 m distance from each other. Recorded acoustic intensity time series showed a clear direct blast signal (having the shape of the emitted pulse) followed by an about 30 second duration long reverberation coda. We show that, for consistent model-data comparison, considering a combined effect of several mechanisms is needed, each dominating within its own time interval or segment. The direct signal, corresponding to a short-range nearly horizontal propagation, is strongly affected by the presence of a weak near-surface (within 50 m depth) acoustic channel, refraction effects in the water gradient layer and reflection from the ice cover. Potentially, analysis of the direct arrival at ranges where focusing effects of upward refraction become noticeable may provide a base for estimating parameters of the surface duct and its boundaries, the ice cover and the gradient layer, and observing their dynamics. Reverberation coda that follows the direct signal corresponds to medium-range bottom- and ice-bounced arrivals from steep angles which are controlled by reflectivity and scattering strengths of ice and bottom, their physical properties, and acoustical parameters. A final comparison of the ICEX14 data with modeling results includes summation of short and medium-range mechanisms, which provides both qualitative and quantitative explanation for the whole time series.
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