Temporal variability of the core depth of EUC in the Gulf of Guinea

The Gulf of Guinea is an important region in the tropical Atlantic by virtue of its geographical position with a closed boundary to the north and an open South Atlantic Ocean to the south. This leads to a direct impact on local oceanic and atmospheric forcings. Equatorial Kelvin waves bring sub-thermocline waters to the near surface, where the thermocline was already shallow. At the same time, freshening from river runoff and upwelling changes the density structure considerably. We use Argo data, Sea Surface Height (SSH) from altimetry and winds from scatterometers to study changes in water properties in the region. We characterise the core depth of the equatorial undercurrent (EUC) to observe changes at sub-seasonal to annual time scales at four different chosen areas in the region. We further examine the impact of remote forcing with a view to understanding its influence on the core depth of the EUC and the resulting consequence to local oceanic and atmospheric circulation. Results show that the EUC shallows east of the Guinea Gulf, and south of the equator at the beginning of June as the monsoon winds strengthens. The core depth variability show annual and sub-seasonal cycles which are also reproduced by the SSH data.