The SeSaM Project: Sargassum Forecasting and its Integration into the Digital Twin of the Ocean

The SeSaM (Seasonal Sargassum Monitoring and Forecasting) project addresses the critical challenge of managing mass sargassum invasions in the Tropical Atlantic Ocean, providing key insights and forecasting tools for stakeholders. Mercator Ocean International has operationalized the NEMO-based model of sargassum distribution, initially developed by the French National Research Institute for Sustainable Development (IRD). Integrated into the NEMO4.2 framework, the model enables 7-month ensemble forecasts of the physical ocean (SST, currents) and the related sargassum distribution using initial conditions derived from Sentinel-3/OLCI satellite data provided by CLS (Collecte Localisation Satellites). The system delivers reliable predictions of Sargassum transport and seasonal evolution. Forecasts for 2020–2025 are accessible through the project platform. By 2025, these forecasts will also be available on the Digital Twin of the Ocean (DTO), through the EDITO platform (European DTO) with monthly updates. Future enhancements will include interactive user services within the DTO, enabling "what-if" scenarios to optimize collection strategies and support informed decision-making. This initiative is a key step toward mitigating the ecological and socio-economic impacts of Sargassum influxes while exploring its potential as a resource.