Regional Circulation at the Central-East of Macaronesia from a High Resolved Configuration with Symphonie (3D Hydrodynamic Model)

Globally, a significant number of ocean models allow the study of various physical processes and large-scale ocean-atmosphere exchanges. In some regions, the current resolutions of available global and regional models remain relatively low and can therefore restrict the feasibility of many studies involving marine circulation and its impact on biogeochemical interactions, as well as some population dynamics, which require both fine spatial and high temporal resolution. Located in the Northeast Atlantic Ocean, Macaronesia is one such region, where the global ocean model and the regional Atlantic-Iberian Biscay Irish (IBI) model, both provided by Copernicus (https://data.marine.copernicus.eu/products?q=ibi) , with resolutions of 1/12° (~8 km) and 1/36° (~3 km) respectively, may remain low to reproduce coastal circulation locally in this area full of archipelagos. This region presents a fairly complex circulation linked to (i) Mesoscale activities and it is part of the (ii) Canary Coastal Upwelling system in the Northwest African coastal zone (between Mauritania and Morocco), among the most productive in the world. Improving the available configurations for this region could allow further investigations into these physical processes, among many others. This study proposes a parameterized 3D configuration using SYMPHONIE Model (https://sirocco.obs-mip.fr/ocean-models/s-model/) in Central East of Macaronesia (which includes the Canary Islands, Madeira and Selvagens archipelagos). The configuration is implemented on a horizontal curvilinear Arakawa C-grid, which integrates very high-resolution bathymetry in coastal areas (~100 m, IHM of Spain and EMODNET) and ~400 m offshore (GEBCO data). This horizontal grid provides a resolution of approximately ~400 m locally in all coastal areas of the domain and a maximum of 2 km offshore. The water column is discretized on 40 vertical levels using the Vanishing Quasi Sigma (VQS) system. The model is forced at its boundaries by daily global ocean conditions (SSH, SST, SSS) from the Copernicus CMEMS global Reanalysis system at a resolution of 1/12° (~8 km) and atmospheric forcings come from daily ECMWF analyses at a resolution of 1/8° (~13.5 km). The tide is taken into account in this configuration, thanks to the FES2014 model at 1/16° resolution (~6.8 km). Simulated over 3 consecutive years (June 2022 – July 2025), this new configuration offers hourly averaged fields of ocean variables (SSH, SST, SSS) and currents at a very high spatial resolution (~400 m to 2 km). The evaluation of this configuration is initially carried out spatially by comparing it with (i) satellite observation data, and then (ii) ponctual stations extracted from the model are compared with observations from ARGO profilers. In order to estimate whether the increased spatio-temporal resolution of this new configuration improves the representation of dynamics in this region, the fields from Symphonie are compared with the global (~8 km) and the regional IBI (~3 km) reanalyses. This increased resolution provided a better representation for regional and coastal circulation patterns and made it possible to study marine connectivity through larval dispersal of several benthic populations predominantly found around those archipelagos.

Keywords : Regional Circulation, Macaronesia, CMEMS Copernicus, Global Ocean - Atlantic-Iberian Biscay Irish Models, Satellite Observations, Argo Profilers, Marine Connectivity, Symphonie.