Assessment of the Finite-volumE Sea ice-Ocean Model (FESOM2.0) – Part 1: Description of selected key model elements and comparison to its predecessor version

• Published in: Geoscientific Model Development
• Main Authors: Scholz, Patrick, Sidorenko, Dmitry, Gurses, Ozgur, Danilov, Sergey, Koldunov, Nikolay, Wang, Qiang, Sein, Dmitry, Smolentseva, Margarita, Rakowsky, Natalja, Jung, Thomas
• Format: Text
• Language: English
• Published: 2019
• Subjects: Sea ice
• Online Access: https://doi.org/10.5194/gmd-12-4875-2019; https://gmd.copernicus.org/articles/12/4875/2019/

The evaluation and model element description of the second version of the unstructured-mesh Finite-volumE Sea ice-Ocean Model (FESOM2.0) are presented. The new version of the model takes advantage of the finite-volume approach, whereas its predecessor version, FESOM1.4 was based on the finite-element approach. The model sensitivity to arbitrary Lagrangian–Eulerian (ALE) linear and nonlinear free-surface formulation, Gent–McWilliams eddy parameterization, isoneutral Redi diffusion and different vertical mixing schemes is documented. The hydrographic biases, large-scale circulation, numerical performance and scalability of FESOM2.0 are compared with its predecessor, FESOM1.4. FESOM2.0 shows biases with a magnitude comparable to FESOM1.4 and simulates a more realistic Atlantic meridional overturning circulation (AMOC). Compared to its predecessor, FESOM2.0 provides clearly defined fluxes and a 3 times higher throughput in terms of simulated years per day (SYPD). It is thus the first mature global unstructured-mesh ocean model with computational efficiency comparable to state-of-the-art structured-mesh ocean models. Other key elements of the model and new development will be described in follow-up papers.