A multi-scale approach to model ice mélange

The continuum viscous-plastic sea-ice model is widely used in climate models for simulating large-scale sea-ice dynamics, usually on grids of several kilometres (> 10km). Recently, there is an increasing interest in modelling small-scale processes that have the potential to impact large-scale dynamics, such as sea-ice iceberg interactions in the context of ice mélange. Ice mélange has not yet been studied in the context of climate models as efficient numerical realizations are missing. To close this gap, we present a hybrid ice-mélange model. In this approach, icebergs in form of particles are coupled to the viscous-plastic sea-ice model by modifying the tensile strength in the presence of icebergs. The icebergs, in the size of several hundreds of meters, are tracked on a subgrid scale, which makes the approach numerically efficient. Based on a series of idealised test cases, we demonstrate that this approach captures relevant small-scale physics such as polynya formation caused by grounded icebergs.