Mechanical diffusion in grease ice stirred by gravity waves

The possibility of hydrodynamic diffusion in a model of grease ice stirred by the velocity field of a gravity wave is explored. It is argued that mechanical interactions among ice crystals can induce disturbances in the fluid velocity - in the form of interstitial flows - analogous to those leading to diffusion in fixed beds. A two-fluid description of the system is introduced, in which the ice matrix is treated as a deformable porous medium. Depending on the range of parameters, the effective diffusivity of the medium can exceed the value which would be obtained by only keeping into account particle dislocation induced by contact interactions.