Planetary trapped waves drive intercontinental and trans-basin oceanic teleconnections between South America and Africa

Oceanic coastal trapped waves transmit energy over long distances and influence coastal variability, affecting sea level, currents, temperature, and nutrient fluxes, with consequences for marine ecosystems. Previous studies in the tropical Atlantic have demonstrated the conversion of equatorial Kelvin waves into coastal trapped waves at the eastern boundary. However, the connection between the western tropical Atlantic and the equatorial band has received less attention. Here, we identify an intercontinental oceanic teleconnection linking South America and Africa through the equatorial and coastal waveguides in the Atlantic using a global ocean reanalysis. Intraseasonal (40-130 days) coastal trapped waves propagate northward along the South American coast and occasionally reach the equator, where they convert into equatorial Kelvin waves. These signals cross the basin and subsequently generate coastal trapped waves along the African coast, forming a continuous trapped-wave corridor connecting the continental margins. Episodically, the connection extends further, with waves traced back to the equatorial Pacific. Coastal trapped wave activity exhibits strong seasonal and interannual modulation, controlled by background circulation and large-scale atmospheric forcing associated with the Madden-Julian Oscillation, ENSO, and the Antarctic Oscillation. Our results reveal an unreported pathway for oceanic connectivity across the tropical Atlantic, with potential implications for Atlantic Niño preconditioning. A continuous pathway for oceanic trapped waves bridges the Atlantic basin, linking the South American and African coast, according to analyses of sea surface height data.