A Hybrid Ice Model

ABSTRACT 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 (10 km). 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. The latter have not yet been studied in the context of climate models as efficient numerical realizations are missing. To close this gap, a hybrid ice‐mélange model has been introduced recently. In the 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 metres, are tracked on sub‐grid scale, which makes the approach numerically efficient. In this contribution, we extent the work to a setup that treats both sea‐ice floes and icebergs as particles. We refer to this model framework as the hybrid ice model . We show that the time discretized momentum equation is equivalent to a convex energy minimization problem and therefore allows the use of efficient numerical solvers. Furthermore, we demonstrate that sub‐grid dynamics, such as polynya formation due to grounded icebergs, can be reflected with a full particle representation of the sea‐ice tracers.