Modelling Hydrodynamic Circulation Patterns in the Bight of Benin Using ROMS

Understanding the three-dimensional hydrodynamic circulation of the Bight of Benin is essential for predicting the fate of oil spills, managing fisheries productivity, and evaluating climate-driven coastal changes in the eastern Gulf of Guinea. This study implements the Regional Ocean Modelling System to simulate the seasonal and sub-seasonal circulation patterns of the Bight of Benin, calibrated and validated against observed sea surface temperature, salinity, and current data from research cruises and moored instruments. The model domain encompasses the Nigerian shelf from Lagos to the Cross River estuary and extends 400 kilometres offshore to the 2000-metre isobath. Atmospheric forcing is provided by ERA5 reanalysis products, and lateral boundary conditions are derived from the Copernicus Marine global model. Model sensitivity experiments isolate the relative importance of wind forcing, coastal geometry, and buoyancy fluxes from the Niger Delta river discharge in shaping the seasonal circulation. The study fills a critical observational gap by resolving the previously poorly characterised summer reversal of the Guinea Current and its interaction with the seasonal cold tongue upwelling. Taylor diagrams, root mean square difference, and skill score metrics quantify model performance against independent validation datasets. Results are expected to demonstrate adequate skill in reproducing the timing and intensity of upwelling events and the spatial structure of salinity fronts. Hydrodynamic output is used to drive particle tracking simulations that trace the dispersal pathways of oil released from three major offshore platform locations. Keywords: hydrodynamic modelling, ROMS, Bight of Benin, Guinea Current, upwelling simulation