FESOM2 - global ocean modeling on unstructured meshes. Recent developments.
High computational power is clearly needed in studies relying on the modeling of physical processes in the ocean. Since the first internal Rossby radius is decreasing in high latitudes down to several kilometers or even less on the ocean shelves, very fine meshes are needed to simulate the emerging eddy dynamics. Recently developed large-scale ocean circulation models, formulated on unstructured meshes, such as FESOM2, make it possible to utilize more flexible meshes with variable resolution. By increasing resolution only in energetically active regions, this allows resolving ocean eddies in global setups at a small computational cost. We will introduce Finite-volumE Sea ice-Ocean circulation Model, Version 2.0 (FESOM2), the first mature global model of its kind formulated on unstructured meshes, and discuss its performance in the global coupled and stand-alone eddy-resolving simulations and regional simulations down to 1 km scale. We will also present the analysis of the model performance with a focus on bottlenecks in parallel scalability. This analysis suggests that unstructured-mesh models are becoming extremely competitive tools in high-resolution climate modeling.