Model study of ocean wave propagation through broken sea ice covers with variable ice concentration

A theoretical model is used to study the propagation of water waves into and through the marginal ice zone. The marginal ice zone is modelled as a region composed of thin floating elastic plates separated by open water gaps, with randomly chosen lengths. The impact of the marginal ice zone on incoming waves is determined using a reconstruction of the dominant wavelength and attenuation rate, and a transferred amplitude (measuring the change in amplitude at the ice edge), and these quantities are studied for different ice concentrations (the areal fraction of ice cover to open water). For all concentrations, the model is shown to predict a deterministic limit for ice covers composed of floes and gaps much smaller than wavelengths, where the wave fields are independent of the particular realisation of the ice cover and insensitive to further reduction in floe and gap lengths (called the small floe–gap limit). The obtained small floe–gap limit is replicated by using a periodic ice cover that supports damped Bloch waves. The model predicts that as concentration decreases, the wavelength increases and the transferred amplitude and attenuation rate decrease, with attenuation rate scaling with ice concentration. • Developed a model of wave propagation in ice covers with random variations in floe and open water gap lengths, to investigate effect of ice concentration. • Obtained semi-analytic expressions for all wave properties in the small floe–gap limit, which agree with ensemble averages over realisations of random ice covers. • Attenuation in the small floe–gap limit is found to scale with concentration for all investigated wave frequencies.