Abstract
The marginal ice zone is a highly dynamical region where sea ice and ocean waves interact. Large-scale sea ice models only compute domain-averaged responses. As the majority of the marginal ice zone consists of mobile ice floes surrounded by grease ice, finer-scale modelling is needed to resolve variations of its mechanical properties, wave-induced pressure gradients and drag forces acting on the ice floes. A novel computational fluid dynamics approach is presented that considers the heterogeneous sea ice material composition and accounts for the wave-ice interaction dynamics. Results show, after comparing three realistic sea ice layouts with similar concentration and floe diameter, that the discrepancy between the domain-averaged temporal stress and strain rate evolutions increases for decreasing wave period. Furthermore, strain rate and viscosity are mostly affected by the variability of ice floe shape and diameter.
Highlights
The region where ocean processes affect sea ice, known as marginal ice zone (MIZ; [1]), is a highly complex system [2,3,4] during the ice formation and melt season
We focus on the pancake and grease ice rheology variables over short time periods (
We presented a new numerical approach to model the small-scale interaction of waves, pancake ice floes and interstitial grease ice
Summary
The region where ocean processes affect sea ice, known as marginal ice zone (MIZ; [1]), is a highly complex system [2,3,4] during the ice formation and melt season. Most contemporary dynamic-thermodynamic sea ice models used for predicting global climate are phenomenological large-scale models (order of 100 km [5]) in which internal stresses are related to the strain rate via a viscous-plastic rheology [6,7,8] These models adopt a smeared approach in which an area with heterogeneous ice characteristics (fractures, leads, open water and different ice types) is modelled as a single homogeneous material with averaged properties, and in which ice-ocean interactions are parameterised [9]. Dynamic-thermodynamic sea ice models on a floe-scale are scarce [12], in particular with respect to the characteristic pancake ice floes found in the winter MIZ. External forcing in terms of in-plane wind and ocean current stress vectors applied to the ice is represented by τa and τo, respectively. Where τsd is the viscous component representing the skin drag acting on the entire ice-ocean interface and τf k the Froude–Krylov force due to the wave pressure field acting on the ice floe circumference. The air density, ice-air drag coefficient and wind turning angle are indicated by ρa, Ca and θa, respectively
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