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When modeling gravity wave propagation through an array of discrete ice floes, considered as a homogenous elastic continuum, the equivalent elasticity is less than the intrinsic material elasticity of ice. The array behaves increasingly like a collection of rigid floating masses when the floe sizes decrease. Extending a former wave flume experiment with polyethylene plates (Sakai & Hanai, 2002, https://web2.clarkson.edu/projects/iahrice/IAHR%202002/Volume%202/189.pdf), we conducted an experiment with saline ice floes at the Hamburg Ship Model Basin (HSVA). Using the measured wave number and the dispersion relation from a continuous elastic plate theory, we determine the equivalent elasticity. Parallel theoretical solutions are obtained using the matched eigenfunction expansion method (Kohout et al., 2007, https://doi.org/10.1016/j.jfluidstructs.2006.10.012), assuming ice floes as an array of thin elastic plates floating over inviscid water. Despite data scatter in laboratory tests, the celerity (phase speed) from the laboratory and theoretical results both show a decreasing trend when the floe size reduces. The corresponding equivalent elastic modulus decreases from the intrinsic modulus to zero. The matched eigenfunction expansion method is then applied to investigate cases under field conditions. Using all the theoretical results, an empirical relation is proposed for the equivalent elasticity in terms of wavelength, floe size, and length scale from the intrinsic elasticity of the floes. In addition to celerity, wave amplitude along the ice cover is compared with the theoretical results. Large discrepancies of wave attenuation from laboratory and theoretical solutions are found, indicating that attenuation mechanisms other than wave scattering need to be considered. Plain Language Summary: Ocean wave forecasts in the ice‐covered seas require reliable modeling of ice effect on wave propagation. The wave dispersion and damping rate due to the ice cover are different from the propagation in open water. One way is to consider the total effect of a field of fragmented ice floes as one continuous elastic sheet. However, the elasticity of the sheet is not measurable directly, which could be much lower than the intrinsic elasticity of ice. In this study, we examine a single‐period wave propagating through an array of ice floes using both physical measurement and a theoretical approach. We analyze data from two laboratory experiments and the parallel theoretical studies. The theoretical studies are also extended into field scales using parameters collected from two field experiments. By assimilating all results, we determine the dependence of the equivalent elasticity of the sheet on the floe size. Furthermore, the surface undulation due to free edges makes the attenuation measurement challenging. Despite this difficulty, extra damping beyond wave scattering is observed. Key Points: Wave celerity (phase speed) and amplitude over an array of ice floes are obtained from laboratory tests and theoretical solutionsBoth show celerity decreases as floe size decreases, while decay of amplitudes in laboratory data is generally higherAn empirical formula for the equivalent elasticity of an array of floes is derived from wave numbers obtained in the theoretical results [ABSTRACT FROM AUTHOR]

Abstract: The ability of viscous layer models to describe the attenuation of waves propagating in grease‐pancake ice covered ocean is investigated. In particular, the Keller's model (Keller, ; https://doi.org/10.1029/97JC02966), the two‐layer viscous model (De Carolis & Desiderio, ; https://doi.org/10.1016/S0375-9601(02)01503-7) and the close‐packing model (De Santi & Olla, ; arXiv:1512.05631) are extensively validated by using wave attenuation data collected during two different field campaigns (Weddell Sea, Antarctica, April 2000; western Arctic Ocean, autumn 2015). We use these data to inspect the performance of the three models by minimizing the differences between the measured and model wave attenuation; the retrieved ice thickness is then compared with measured data. The three models allow to fit the observation data but with important differences in the three cases. The close‐packing model shows good agreement with the data for values of the ice viscosity comparable to those of grease ice in laboratory experiments. For thin ice, the Keller's model performance is similar to that of the close‐packing model, while for thick ice much larger values of the ice viscosity are required, which reflects the different ability of the two models to take into account the effect of pancakes. The improvement of performance over the Keller's model achieved by the two‐layer viscous model is minimal, which reflects the marginal role in the dynamics of a finite eddy viscosity in the ice‐free layer. A good ice thickness retrieval can be obtained by considering the ice layer as the only source in the wave dynamics, so that the wind input can be disregarded. [ABSTRACT FROM AUTHOR]

This paper presents a wave-in-ice model calibration study. Data used were collected in the thin ice of the advancing autumn marginal ice zone of the western Arctic Ocean in 2015, where pancake ice was found to be prevalent. Multiple buoys were deployed in seven wave experiments; data from four of these experiments are used in the present study. Wave attenuation coefficients are calculated utilizing wave energy decay between two buoys measuring simultaneously within the ice covered region. Wavenumbers are measured in one of these experiments. Forcing parameters are obtained from simultaneous in-situ and remote sensing observations, as well as forecast/hindcast models. Cases from three wave experiments are used to calibrate a viscoelastic model for wave attenuation/dispersion in ice cover. The calibration is done by minimizing the difference between modeled and measured complex wavenumber, using a multi-objective genetic algorithm. The calibrated results are validated using two methods. One is to directly apply the calibrated viscoelastic parameters to one of the wave experiments not used in the calibration and then compare the attenuation from the model with measured data. The other is to use the calibrated viscoelastic model in WAVEWATCH III® over the entire western Beaufort Sea and then compare the wave spectra at two remote sites not used in the calibration. Both validations show reasonable agreement between the model and the measured data. The completed viscoelastic model is believed to be applicable to the fall marginal ice zone dominated by pancake ice. [ABSTRACT FROM AUTHOR]

Wave attenuation from two field experiments in the ice-covered Southern Ocean is examined. Instead of monotonically increasing with shorter waves, the measured apparent attenuation rate peaks at an intermediate wave period. This 'rollover' phenomenon has been postulated as the result of wind input and nonlinear energy transfer between wave frequencies. Using WAVEWATCH III®, we first validate the model results with available buoy data, then use the model data to analyze the apparent wave attenuation. With the choice of source parameterizations used in this study, it is shown that rollover of the apparent attenuation exists when wind input and nonlinear transfer are present, independent of the different wave attenuation models used. The period of rollover increases with increasing distance between buoys. Furthermore, the apparent attenuation for shorter waves drops with increasing separation between buoys or increasing wind input. These phenomena are direct consequences of the wind input and nonlinear energy transfer, which offset the damping caused by the intervening ice. [ABSTRACT FROM AUTHOR]