Sea-Ice Dynamics on Unstructured Voronoi Meshes in MPAS-Seaice
The sea-ice dynamics of CICE were adapted from the regular structured quadrilateral mesh used there, to the unstructured Voronoi tessellation meshes used by the Modeling for Prediction Across Scales framework and by the Energy Exascale Earth System Model (E3SM).
The unstructured Voronoi tessellation formulation of sea ice dynamics developed here allows model resolution to be focused in regions of interest allowing higher resolution simulations to be performed in these regions.
A sea ice dynamical core has been developed for the Model for Prediction Across Scales (MPAS) framework, that uses the variational formulation of the spatial operators employed in the CICE model, but adapted for the polygonal grid cells found in MPAS meshes. This sea ice dynamical core is used by the MPAS-Seaice model, the sea ice component of the Energy Exascale Earth System Model (E3SM). The use of the MPAS mesh, with its Voronoi tessellated cells, allows model resolution to be focused on areas of interest, increasing the model resolution achievable for a given amount of computational resources. The MPAS mesh also allows the removal of equatorial grid cells, where sea ice does not form, increasing computational efficiency and load balancing, while also being flexible enough to allow quadrilateral meshes to still be used. The new dynamical core was validated with a series of idealized test cases examining the error convergence of the spatial operators with increasing resolution, with comparison simulations comparing model output with results from simulations with CICE, and against sea ice observations.