Sea ice models used in the MyOcean Marine Core Services are all based on the viscous-plastic (VP) or the elastic-viscous-plastic (EVP) sea ice rheology and all neglect the effects of waves, which are extremely important in the marginal ice zone (MIZ). In this portion of the ice cover sea ice dynamics and thermodynamics are ill-defined, causing a significant deterioration in the quality of sea ice forecasts in the MIZ.
Interactions of waves and sea ice in the MIZ have been well observed and conceptual models have been proposed. Ocean waves fragment large floes into smaller ones and make them collide with each other so that the large-scale dynamical response of sea ice to atmospheric and oceanic forcings is no longer that of a viscous-plastic material. Collisional rheologies have been proposed to better simulate the behaviour of sea ice in the MIZ but none of these models have been tested in realistic situations nor included in ice-ocean coupled systems.
Figure: Example showing the effects of the 2012 Arctic summer storms waves in TOPAZ, significant wave high SWH (left) and maximum floe size Dmax (right).
Recently, a collisional rheology has been included in a sea ice-ocean model (NERSC/HYCOM) and tested it in a high-resolution configuration. Simulations showed that the combination of a collisional rheology with an EVP rheology is possible and would definitely improve the predictions for ice behaviour in the MIZ. By combining the collisional rheology with a waves-in-ice model (WIM) forced by an external wave model (WP2) the rapidly changing dynamical properties in the MIZ may be represented.