Elastic parabolic equation and normal mode solutions for seismo-acoustic propagation in underwater environments with ice covers

Abstract

Sound propagation predictions for ice-covered ocean acoustic environments do not match observational data: received levels in nature are less than expected, suggesting that the effects of the ice are substantial. Effects due to elasticity in overlying ice can be significant enough that low-shear approximations, such as effective complex density treatments, may not be appropriate. Building on recent elastic seafloor modeling developments, a range-dependent parabolic equation solution that treats the ice as an elastic medium is presented. The solution is benchmarked against a derived elastic normal mode solution for range-independent underwater acoustic propagation. Results from both solutions accurately predict plate flexural modes that propagate in the ice layer, as well as Scholte interface waves that propagate at the boundary between the water and the seafloor. The parabolic equation solution is used to model a scenario with range-dependent ice thickness and a water sound speed profile similar to those observed during the 2009 Ice Exercise (ICEX) in the Beaufort Sea.

Ambient Noise in the Canadian Arctic

“…Recent advances allowed a fully elastic seabed and ice canopy to be incorporated into a PE simulation (Collins 2012(Collins , 2015. Collis et al (2016) benchmarked such a model against an elastic normal mode code and wave number integration solution and demonstrated the PE model's ability to compute transmission loss under a slowly varying range-dependent ice thickness. Collins et al (2019) was further able to demonstrate scattering from a data-derived ice surface with keels using a fully elastic PE code over a model range of 40 km.…”

Temporal and spatial dependence of a yearlong record of sound propagation from the Canada Basin to the Chukchi Shelf

“…Acoustic propagation models to calculate the sound pressure field under sea ice have been studied for decades, and a variety of techniques have been proposed, including analytical (Diachok, 1976;Twersky, 1957) and approximate scattering models (Hope et al, 2017;Kudryashov, 1996;LePage and Schmidt, 1994), as well as modal approaches (Ballard, 2019;Gavrilov and Mikhalevsky, 2006), parabolic equation (PE) models (Collins, 2015;Collins et al, 2019;Collis et al, 2016;Woolfe et al, 2016), ray models (Sagers et al, 2015), finite element (Simon et al, 2018) and finite difference methods (Frick, 1991). The approaches can be divided into two broad classes: those that model interaction with the sea canopy using a reflection coefficient that encompasses both the average physical properties of the sea ice and statistics of its roughness, and those that model the full field using realizations of the sea ice that include its inhomogeneous internal properties and range-dependent topography.…”

SH Seismoelectric Response of a Glacier: An Analytic Study

“…Concerning the choice of the source, on the one hand, we have proved in a previous work (Zyserman et al, 2017a) that the signal-to-noise ratio can be higher in this case than when using compressional sources, and on the other hand, although up to now this kind of sources has not been used in seismoelectric field studies, they have been employed successfully in several works aiming to characterize the shallow subsurface (Beilecke et al, 2016;Comina et al, 2017;Konstantaki et al, 2013;Konstantaki et al, 2015;Prior et al, 2017;Stucchi et al, 2017). The ice forming the glacier is treated as an elastic medium; this is a common assumption when performing seismic studies (Collins et al, 2016;Podolskiy & Fabian, 2016;Presnov et al, 2014b;Presnov et al, 2014a).…”

“…The vacuum permittivity is taken to be 0 = 8.85 × 10 −12 F/m. a These values are taken from Collins et al (2016). b These values are given in Petrenko and Whitworth (1999).…”