Waves Forcing Climate on Bénin Coast, and the Link with Climatic Index, Gulf of Guinea (West Africa)

Hounguè, G.H.; Kounouhéwa, B.B.; Almar, R.; Sohou, Z.; Lefebvre, J-P.; Houépkonhéha, M., and Tokpohozin, B., 2018. Waves forcing climate on Bénin coast, and the link with climatic index, Gulf of Guinea (West Africa). In: Almar, R.; Almeida, L.P.; Trung Viet, N., and Sall, M. (eds.), Tropical Coastal and Estuarine Dynamics. Journal of Coastal Research, Special Issue No. 81, pp. 130–137. Coconut Creek (Florida), ISSN 0749-0208. Bénin's coastline is currently undergoing very marked erosion. This erosion is the consequence of the impact of swells from the South Atlantic and is accentuated by human development. These swells, from weak to moderate energies, drive Bénin's coastline evolution. Although crucial, the characteristics of this forcing are not accurately defined. From instantaneous outputs of ERA40 and ERA-Interim's sea state parameters, the annual and seasonal average of significant wave height (Hs), peak period (Tp) and direction (Dir) were determined to characterize wave forcing and extreme event on Bénin Coast after a validation using the data of the ALIZEE buoy installed 6 km off the coast of Bénin in December, 2015. Hindcast data analysis indicates an important if increasing trend of Hs and Tp. A weak trend of peak direction towards the South West clockwise is observed between 1957 and 2016. The intra-annual variability of Hs shows a marked seasonality, the first one characterized by strong swells from April to October and the second one by moderate swells from October to April. Offshore wave height is positively correlated with AMO (Atlantic Multidecanal Oscillation).