Model-data comparison of sound propagation in a glacierized fjord with a brash ice top surface

Transmission loss measurements were conducted in the meltwater-modified surface layer near Hansbreen Glacier in Hornsund Fjord in southwestern Svalbard in September 2017 [Deane and Glowacki, JASA 143, 1711 (2018)]. An ITC-1007 (International Transducer Corporation) source emitting an m-sequence signal (149 dB re 1 µPa, 11 kHz carrier frequency) was tethered at 6.7 m depth to a boat allowed to drift 20 m to 200 m from a pair of stationary receivers. These two receivers, HTI-96-Min hydrophones (High Tech, Inc.), were tethered at 8 and 17 m to a buoy anchored 500 m from the glacier terminus. Within this environment, and typical for a glacierized fjord, regular calving events contributed to a collection of icebergs, or brash ice, at the water surface obstructing the transmission path, particularly the surface reflected path. A ray-based approach using Bellhop, a code available in the Acoustics Toolbox, was used to simulate the environment as a means of comparison to the measured data. The variability of the brash ice surface was included in the model through incorporating a simulated surface at the ocean surface. Comparisons between outcomes from increasingly complex iterations of this model with the collected data are discussed.