Submitted as: model evaluation paper
05 Oct 2023
Submitted as: model evaluation paper |  | 05 Oct 2023
Status: this preprint is currently under review for the journal GMD.

CAR36, a regional high-resolution ocean forecasting system for improving drift and beaching of Sargassum in the Caribbean Archipelago

Sylvain Cailleau, Laurent Bessières, Léonel Chiendje, Flavie Dubost, Guillaume Reffray, Jean-Michel Lellouche, Simon van Gennip, Charly Régnier, Marie Drevillon, Marc Tressol, Matthieu Clavier, Julien Temple-Boyer, and Léo Berline

Abstract. The stranding of sargassum seaweed on the Caribbean Archipelago beaches constitutes a real socio-economic, ecological and health problem. Météo-France currently operates a model of sargassum drift forecasts (called MOTHY) forced by ocean currents from the global analysis and forecasting system GLO12 at 1/12° (~ 9 km over the Caribbean) operated by Mercator Ocean International (MOi). In order to improve the Météo-France drift forecast, MOi has developed a regional high-resolution ocean forecasting system CAR36 at 1/36° (~ 3 km) centred on the Caribbean Archipelago region. In addition to a finer spatial resolution, this system was designed to resolve some higher frequency signals such as the tidal forcing and to use hourly atmospheric forcing including the inverse barometer effect.

Here the added value of the CAR36 system relative to GLO12 is evaluated with particular focus on the reproduction of meso- and sub-mesoscale structures representing key features of the Caribbean region dynamics and therefore sargassum transport. The realism of the local dynamics was examined with standard statistical validation diagnostics using satellite data (Sea Surface Height, Sea Surface Temperature, Sargassum detection) and drifting buoys, together with more process-oriented diagnostics such as eddy detection and tracking across the domain.

GLO12 and CAR36 hindcast simulations were compared over the year 2019. CAR36 showed marginally better scores using OceanPredict diagnostics ( The dynamics of a westward-propagating North Brazil Current (NBC) eddy from its entry into the domain to its dissipation was found to be more realistic in CAR36, especially at the end of its lifetime when it collides with the Caribbean Archipelago. The transfer of kinetic energy from the eddy dissipating westward into the Caribbean Sea was diagnosed as more pronounced for CAR36 corresponding to filamentary structures crossing the Caribbean Archipelago and resulting in part from the friction of the NBC eddy along the islands to the east. Using detection from satellite, aggregation of Sargassum around eddies or along filaments suggests that CAR36 should be able to improve the algae drift forecasts.

Sylvain Cailleau et al.

Status: open (until 09 Dec 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CEC1: 'Comment on gmd-2023-183', Juan Antonio Añel, 19 Nov 2023 reply
    • AC1: 'Reply on CEC1', Sylvain Cailleau, 23 Nov 2023 reply
  • RC1: 'Comment on gmd-2023-183', Anonymous Referee #1, 06 Dec 2023 reply

Sylvain Cailleau et al.

Sylvain Cailleau et al.


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Short summary
In order to improve the Sargassum drift forecasting in the Caribbean area, drift models can be forced by higher resolution ocean currents. To this goal a 3-km resolution regional ocean model has been developed. its assessment is presented with a particular focus on the reproduction of fine structures representing key features of the Caribbean region dynamics and Sargassum transport. The simulated propagation of a North Brazil Current eddy and its dissipation were found to be quite realistic.