ABSTRACT
Sea ice plays a significant role in the global climate and covers approximately 10% of the earth’s surface (Wilchinsky and Feltham, 2006). Understanding sea ice dynamics and thermodynamics results in better sea ice predictions and therefore a better comprehension of the Antarctic marginal ice zone (MIZ) (Herman, 2016). Large-scale sea ice models, such as Hibler’s viscous-plastic sea ice model, which has been developed to operate successfully at length scales of 10 to 100 kilometer-domain size. The viscous-plastic model by (Hibler, 1979a, Hibler, 1979b) is largely recognised as the standard sea ice dynamics model, which has been widely applied in global climate models. Finer-scale models of sea ice dynamics are scarce (Dansereau et al., 2016), in particular with respect to the characteristic pancake ice found in the Antarctic MIZ. Therefore, the focus in this work is on small-scale modelling of pancake sea ice dynamics. (Hibler, 1979a, Hibler, 1979b) describes a sea ice model in which the internal ice stress and strain rate are related by means of a viscous-plastic sea ice rheology. A large sea ice area, consisting of a fractured surface with different floe sizes and heterogeneous characteristics, is modelled as an isotropic, continuous and homogeneous material (Hutchings et al., 2004). Hibler’s model considers pack ice as a single homogenized material with constant ice density, where ice thickness, ice coverage and ice velocity are the main variables. An existing large-scale numerical model, based on Hibler’s model, has been implemented in the computational fluid dynamics software OpenFOAM by (Bogaers et al., 2018). This paper reports on the modification to the large-scale OpenFOAM model to develop a more detailed small-scale sea ice model, considering a heterogeneous sea ice material composition consisting of separately pancake ice and frazil ice with distinct properties. The thermodynamics of sea ice is neglected, since only small time periods of a few minutes are modelled. Pancake-frazil and pancake-pancake ice interactions are analysed. More realistic atmospheric conditions are applied (Mehlmann and Richter, 2017), including wind, current and wave loading. Average stress, strain rate and viscosities are obtained.
