Relationship between the equatorial and meridional modes of climatic variability in the tropical Atlantic

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Abstract
The tropical Atlantic Ocean exhibits two primary modes of interannual climate variability: an equatorial mode analogous to, but weaker than, the Pacific El Niño phenomenon, and a meridional mode that does not have a Pacific counterpart. The equatorial mode is responsible for warm (and cold) sea surface temperature (SST) events, mainly in the Gulf of Guinea, and is identifiable by abnormal changes in the equatorial thermocline slope resulting from zonal‐wind anomalies in the western tropical Atlantic. The meridional mode is characterized by a north‐south interhemispheric gradient of SST anomalies. Here it is shown, using observed surface and subsurface oceanic temperatures, that the meridional mode is linked to the equatorial mode, at both decadal and short‐interannual (1–2 years) time scales. Both modes involve north‐south displacements of the ITCZ, as in the annual response.