A Numerical Model of Nonlinearity in Wave Attenuation by Sea Ice

The marginal ice zone (MIZ) is the part of the sea-ice covered ocean closest to the open ocean, with a surface comprising of relatively small floes and open water. It is defined by the presence of ocean surface waves, which attenuate with distance into the MIZ due to interactions with the ice cover. Existing models of wave attenuation in the MIZ are based on linear wave scattering theory. However, recent field experiments show that attenuation depends on wave amplitude in some instances, suggesting that nonlinear contributions are  non-negligible. We present a model of wave interactions with a single ice floe, based on laboratory experimental tests and direct numerical simulations. In the experiments, attenuation of monochromatic waves due to a model floe (a plastic plate) was measured for different wave periods and amplitudes, and floe properties. The numerical simulations use the CFD software OpenFOAM to reproduce the experimental set-up. The experimental and model results are compared and nonlinearity in the attenuation assessed, focusing on processes of wave energy dissipation.