Ocean swell variability along the northern coast of the Gulf of Guinea

This study analyses a 4.5 year (September 2009-March 2014) time-series of remotely-sensed data of altimeter significant wave heights to describe the temporal and spatial variability of ocean swells along the northern coast of the Gulf of Guinea. The NOAA WAVEWATCH III (NWW3) wave model data were used with altimeter data to determine the origin of the swells that occur along the coast of Cote d'Ivoire in West Africa. We show that the ocean swells along the northern coast of the Gulf of Guinea are generated in the Southern Ocean and then propagate from south to north in the South Atlantic Ocean, before turning south-west to north-east close to the coast. This finding corroborates previous studies in this area. The remotely-sensed and NWW3 significant wave height data captured the strong swells observed along the coast of Cote d'Ivoire from the period 28 August-3 September 2011, which were responsible for an extreme erosion event of more than 12 m along that country's coastline. This extreme event was triggered by a strong storm in the region between 40 degrees and 60 degrees S that occurred eight days previously in the South Atlantic. The waves propagated as swells at a speed of about 875 km day(-1) before reaching the northern African coast.