Variability and Dynamics of the Tropical Atlantic Ocean

The Tropical Atlantic Ocean exhibits a rich spectrum of variability spanning seasonal to decadal time scales, governed by the interplay of wind forcing, ocean currents and wave dynamics. Seasonal changes in trade winds drive the equatorial Atlantic cold tongue and coastal upwelling along West Africa and the southwestern African margin, supplying nutrients to fuel productive ecosystems. Interannual phenomena such as the Atlantic Niño and Benguela Niño arise from anomalies in sea surface temperature and are modulated by equatorial Kelvin waves, coastal trapped waves and remote forcing from other ocean basins. Meridional overturning, the Equatorial Undercurrent and gyre circulations shape heat and salinity distributions, while mixed-layer processes and diapycnal mixing further influence the mean state and its fluctuations. Sea level anomalies along the Gulf of Guinea respond to a combination of remote equatorial forcing and local wind stress, with implications for coastal flooding. Understanding these dynamics is essential for anticipating climate impacts on rainfall patterns, fisheries and carbon cycling across tropical and adjacent regions.

Research from Nature Portfolio

Recent studies have revealed a trans-basin linkage in which a strong Indian Ocean Dipole event preceded an exceptional Benguela Niño by driving high rainfall over the Congo basin. Elevated river discharge formed a low-salinity surface cap that inhibited vertical mixing, allowing sea surface temperatures off southwest Africa to rise more rapidly than usual. In parallel, nearly three decades of satellite altimetry have been used to quantify coastal sea level rise and variability in the Gulf of Guinea, demonstrating an acceleration of mean sea level trends and the propagation of coastally trapped waves in response to both equatorial Kelvin waves and local wind and freshwater fluxes. These findings highlight the critical role of remote forcing and riverine input in modulating tropical Atlantic extremes and coastal hazards.

Variability and Dynamics of the Tropical Atlantic Ocean publication trend

The graph below shows the total number of articles in variability and dynamics of the tropical atlantic ocean across all publications each year (not limited to Nature Index journals).

Technical terms

Equatorial Niño: A warming event in the eastern equatorial Atlantic characterised by positive sea surface temperature anomalies.

Benguela Niño: A coastal warming event off southwest Africa associated with reduced upwelling and anomalous coastal currents.

Equatorial Undercurrent: A subsurface eastward flow along the equator beneath the westward surface currents.

Kelvin wave: A gravity-driven, non-dispersive wave that propagates along the equator or coast with the coast on its right (Northern Hemisphere).

Coastal trapped wave: A wave constrained by rotation and coastline geometry that carries sea level and temperature anomalies poleward.

Nitracline: The depth in the ocean at which nitrate concentration increases sharply with depth.

Thermocline: A layer in the water column where temperature decreases rapidly with depth.

Upwelling: The upward movement of colder, nutrient-rich water from depth to the surface, often driven by wind.

References

1. Indian Ocean Dipole intensifies Benguela Niño through Congo River discharge. Communications Earth & Environment (2024).
2. Sea level variability in Gulf of Guinea from satellite altimetry. Scientific Reports (2024).
3. Impact of Stratospheric Geoengineering on Sea Surface Temperature in the Northern Gulf of Guinea. Climate (2023).
4. Physical drivers of the nitrate seasonal variability in the Atlantic cold tongue. Biogeosciences (2020).
5. Coastal Upwelling Limitation by Onshore Geostrophic Flow in the Gulf of Guinea Around the Niger River Plume. Frontiers in Marine Science (2021).