On the key influence of remote climate variability from Tropical Cyclones, North and South Atlantic mid-latitude storms on the coast of West Africa

The low-lying Senegalese sandy coast is extremely vulnerable to flooding and marine erosion. Using atmospheric reanalyses and wave propagation, we have established the relationships between patterns of climate variability in the Atlantic and wave activity on the Senegalese coast. We show that the significant swells in Senegal are expected to come from the North Atlantic in boreal winter, but more surprisingly also from the South and the Tropical Atlantic in boreal summer. Frontal cyclonic swells have a significant impact on the contribution of sea level to the coast but a limited influence on coastal sediment transport. In contrast, the oblique swells from the South Atlantic have a destabilizing impact on the coast due to the reversal of climatological sediment drift. They also induce significant sea level anomalies on the southern coast of Senegal, the most vulnerable to flooding. This study highlights the importance of studying both regional and large-scale climate variability on wave activity in order to better understand the factors of evolution and vulnerability in coastal areas. In particular, tropical cyclones, which do not have a direct impact (e. g. no heavy rainfall or strong surface winds) on this coastline, have a strong influence on coastal dynamics in Senegal. The methodology of this article can also be applied to many tropical coasts that are under the influence of various wave regimes (e. g. Gulf of Mexico, Pacific, tropical Atlantic islands...). Such studies are therefore crucial for coastal management services, particularly in the context of global warming and the increase in vulnerable coastal populations.