We study the diffusion of ocean waves by floating bodies such as pancakes and
ice floes much smaller than a wavelength. We argue that the combined effect of
hydrodynamic interaction of the ice bodies and inhomogeneities in the ice cover
at scales comparable to that of the wavelength significantly increases
diffusion, producing a contribution to wave attenuation comparable to what is
observed in the field and usually explained by invoking viscous effects. The
resulting attenuation spectrum is characterized by a peak at the scale of the
inhomogeneities in the ice cover, thereby providing a new possible explanation
of the rollover of the attenuation profile at small wavelengths experimentally
observed over the years. The proposed attenuation mechanism has the same effect
as a viscous wave model with effective viscosity linearly dependent on the ice
thickness, which may explain recent findings that viscous wave models require a
thickness-dependent viscosity to fit experimental attenuation data.
Experimental validation is carried out using wave buoy attenuation data and
synthetic aperture radar image analysis.Comment: 29 pages, 5 figure