Seasonal Lagrangian Dynamics of Offshore Pollutant Exposure Along Senegal’s Grande Côte: Implications for Oil and Gas Risk Management

Recent offshore hydrocarbon discoveries along the Senegalese–Mauritanian margin increase the need to quantify oil-spill risk under the highly dynamic circulation of the southern Canary Current upwelling system. We investigate seasonal pollutant dispersion along the Senegalese Grande Côte using Lagrangian particle-tracking experiments forced by outputs from the open-source hydrodynamical ocean model CROCO. The analysis focuses on the role of wind-driven circulation, Ekman transport, and upwelling variability in controlling cross-shore and alongshore transport pathways. Results show a strong seasonal coastal circulation variability. During the cold season (January–May), intensified northerly winds drive coastal upwelling and offshore Ekman transport, enhancing divergence of surface currents and promoting the export of particles away from the coast. This regime limits particle nearshore accumulation but favors broader offshore dispersion over the continental shelf. In contrast, during the warm season (June–September), weakened upwelling-favorable winds and the establishment of anticyclonic circulation north of the Cape induce onshore transport and coastal retention. Particle-release experiments reveal enhanced trapping and accumulation along the Grande Côte during this period. The Kayar region and the Cape Verde Peninsula exhibit relatively higher pollutant exposure during the cold season, whereas the inner continental shelf along the Grande Côte becomes particularly vulnerable during the warm season. These findings suggest that seasonal wind forcing and associated Ekman dynamics have a significant influence on the trajectories of oil spills. Incorporating this variability into contingency planning is essential, as the inner continental shelf of the Senegalese Grande Côte is a dynamically sensitive, high-exposure zone under the warm-season circulation regime.