Coupling the Coastal and Regional Ocean COmmunity model (CROCO) with the Biogeochemical Flux Model (BFM)

With more than 50 variables, the Biogeochemical Flux Model (BFM) is one of the most advanced and complex marine biogeochemical models available. In addition to several phytoplankton and zooplankton groups, it also includes bacterioplankton, and its modular structure allows for the relatively straightforward addition of new plankton functional types (PFT). The BFM is used in the Copernicus Marine Service products for the Mediterranean Sea and these should provide ideal initial and boundary conditions for more detailed regional studies. Here we present the coupling of the BFM with the Coastal and Regional Ocean COmmunity model (CROCO; based on ROMS_AGRIF and SNH). The latter is a non-hydrostatic, terrain-following, free-surface ocean model with a highly efficient time-stepping algorithm, making it very suitable for high-resolution simulations and topographies with a wide range of depths. The models are directly coupled without an intermediate coupler and can be executed in parallel via Message Passing Interface (MPI). We present the results of an idealized case and these are in a good agreement with a similar configuration of a coupled MITgcm-BFM run (Cossarini et al., 2017). Not surprisingly, the coupled system CROCO-BFM proves to be computationally intensive given the large number of variables, and we explore different speed-up possibilities.