Sea-ice dynamics on triangular grids

•Natural coupling between ocean and sea ice model on triangular C-grids.•Stable C-grid type discretization of sea ice dynamics on triangular grids.•Finite element sea ice model on unstructured grids.•Stability analysis of VP and EVP models. We present a discretization of the dynamics of sea-ice on triangular grids. Our numerical approach is based on the nonconforming Crouzeix-Raviart finite element. An advantage of this element is that it facilitates the coupling to an ocean model that employs an Arakawa C-type staggering of variables. We show that the Crouzeix-Raviart element implements a discretization of the viscous-plastic and elastic-viscous-plastic stress tensor that suffers from unacceptable small scale noise in the velocity field. To resolve this issue we introduce an edge-based stabilization of the Crouzeix-Raviart element. Through a blend of theoretical considerations, based on the Korn inequality, and numerical experiments we show that the stabilized Crouzeix-Raviart element provides a stable discretization of sea-ice dynamics on triangular grids that is relevant for sea-ice modelling in ocean and climate science.