Variability of coastal zones in low latitudes (with Application to the Somali Current, the Gulf of Guinea and the EL Nino Current)

Southerly winds in low latitudes drive very intense currents along the western coast and much slower currents along the eastern coast. Just under the surface layer, the currents are opposite to the wind in the eastern part (they flow upwind, following the pressure gradient force); they are in the same direction as the surface flow along the western coast. These different properties are due to the Ekman drift in the surface layer, which is maximal within 3° off the equator and drives strong zonal currents that give outer conditions to coastal currents. Non linearities intensify the western currents but have small effects on the eastern side. When the wind relaxes, southward current appears along the coast. The relevance of these results for the Somali Current, the Gulf of Guinea and the eastern Pacific currents is examined.