Discretization of Sea Ice Dynamics in the Tangent Plane to the Sphere by a CD‐Grid‐Type Finite Element

We present a new discretization of sea ice dynamics on the sphere. The approach describes sea ice motion in tangent planes to the sphere. On each triangle of the mesh, the ice dynamics are discretized in a local coordinate system using a CD‐grid‐like non‐conforming finite element method. The development allows a straightforward coupling to the C‐grid like ocean model in Icosahedral Non‐hydrostatic‐Ocean model, which uses the same infrastructure as the sea ice module. Using a series of test examples, we demonstrate that the non‐conforming finite element discretization provides a stable realization of large‐scale sea ice dynamics on the sphere. A comparison with observation shows that we can simulate typical drift patterns with the new numerical realization of the sea ice dynamics.

Plain Language Summary: Sea ice in polar regions plays an important role in the exchange of heat and freshwater between the atmosphere and the ocean and hence for climate in general. Therefore climate models require a description (a set of equations) to express the large‐scale sea ice motion. We present a mathematical framework for describing sea ice flow in a global three‐dimensional Cartesian system. The idea is to express the sea ice motion in tangent planes. In this reference system, we solve the mathematical equations that describe the sea ice motion. The equations are approximated on a computational grid, that consists of triangles covering the surface of the sphere. On each triangle the sea ice velocity is placed at the edge midpoint. The development is motivated by the infrastructure of the ocean and sea ice model Icosahedral Non‐hydrostatic‐Ocean model. The old representation of sea ice dynamics uses a different design principle. Therefore, the communication between the sea ice and ocean model is computationally expensive. To circumvent this problem we have developed a numerical realization of sea ice dynamics that uses the same infrastructure as the ocean model. We show that the new realization of the sea ice dynamics is capable of capturing the sea ice drift.

Key Points: First realization of sea ice dynamics in tangent planes to the sphere. Discretization of the sea ice dynamics in a three‐dimensional Cartesian framework. Realization of the sea ice dynamics in the ocean and sea ice model Icosahedral Non‐hydrostatic‐Ocean model.

Max Planck Society

DFG

Collaborative Research Center TRR 181

Scientific Steering Committee

http://dx.doi.org/10.17632/2v5shnnmwx

https://mpimet.mpg.de/en/science/modeling-with-icon/code-availability

https://thredds.met.no/thredds/osisaf/osisaf_cdrseaiceconc.html

http://dx.doi.org/10.22033/ESGF/input4MIPs.10842

http://dx.doi.org/10.5067/INAWUWO7QH7B