Submitted as: model description paper 08 Nov 2021

Submitted as: model description paper | 08 Nov 2021

Review status: this preprint is currently under review for the journal GMD.

MPAS-Seaice (v1.0.0): Sea-ice dynamics on unstructured Voronoi meshes

Adrian K. Turner1, William H. Lipscomb2, Elizabeth C. Hunke1, Douglas W. Jacobsena, Nicole Jeffery3, Darren Engwirda1, Todd D. Ringler4, and Jonathan D. Wolfe1 Adrian K. Turner et al.
  • 1Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA
  • 2Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO, USA
  • 3Computer, Computational, and Statistical Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, USA
  • 4Science Technology Policy Institute, Washington, D.C. 20006
  • aformerly Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA

Abstract. We present MPAS-Seaice, a sea-ice model which uses the Model for Prediction Across Scales (MPAS) framework and Spherical Centroidal Voronoi Tessellation (SCVT) unstructured meshes. As well as SCVT meshes, MPAS-Seaice can run on the traditional quadrilateral grids used by sea-ice models such as CICE. The MPAS-Seaice velocity solver uses the Elastic-Viscous-Plastic (EVP) rheology, and the variational discretization of the internal stress divergence operator used by CICE, but adapted for the polygonal cells of MPAS meshes, or alternatively an integral (“weak”) formulation of the stress divergence operator. An incremental remapping advection scheme is used for mass and tracer transport. We validate these formulations with idealized test cases, both planar and on the sphere. The variational scheme displays lower errors than the weak formulation for the strain rate operator but higher errors for the stress divergence operator. The variational stress divergence operator displays increased errors around the pentagonal cells of a quasi-uniform mesh, which is ameliorated with an alternate formulation for the operator. MPAS-Seaice shares the sophisticated column physics and biogeochemistry of CICE, and when used with quadrilateral meshes can reproduce the results of CICE. We have used global simulations with realistic forcing to validate MPAS-Seaice against similar simulations with CICE and against observations. We find very similar results compared to CICE with differences explained by minor differences in implementation such as with interpolation between the primary and dual meshes at coastlines. We have assessed the computational performance of the model, which, because it is unstructured, runs 70 % as fast as CICE for a comparison quadrilateral simulation. The SCVT meshes used by MPAS-Seaice allow culling of equatorial model cells and flexibility in domain decomposition, improving model performance. MPAS-Seaice is the current sea-ice component of the Energy Exascale Earth System Model (E3SM).

Adrian K. Turner et al.

Status: open (until 03 Jan 2022)

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Adrian K. Turner et al.

Adrian K. Turner et al.


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Short summary
We present the dynamical core of the MPAS-Seaice model, which uses a mesh consisting of a Voronoi tessellation with polygonal cells. Such a mesh allows variable mesh resolution in different parts of the domain and the focusing of computational resources in regions of interest. We describe the velocity solver and tracer transport schemes used and examine errors generated by the model in both idealized and realistic test cases and examine the computational efficiency of the model.