Atlantic Niño–ENSO link controlled by SST gradients

A team led by Yunnan University has identified what controls the link between the summer Atlantic Niño and the following winter's El Niño–Southern Oscillation (ENSO), according to a study in The Innovation (2026, vol. 7, issue 10) doi.org. The authors combined more than a century of observations with model sensitivity experiments. They found that sea surface temperature (SST) gradients in the tropical Atlantic and Pacific determine whether the connection is active doi.org.

The relationship has strengthened in recent decades, but its mechanism had remained unclear doi.org. In the observational record, the summer Atlantic Niño and the subsequent winter ENSO were significantly correlated in 1894–1925 and 1984–2009, but not in 1928–1981.

Atlantic zonal and Pacific meridional gradients

The east–west (zonal) SST gradient over the tropical Atlantic is driven by the wind–evaporation–SST (WES) feedback; when the feedback weakens, the gradient weakens as well doi.org. Under weak zonal gradients, the Gill–Matsuno-type response to an Atlantic Niño shows stronger ascending motion over the tropical western Atlantic than under strong gradients doi.org.

Over the eastern tropical Pacific, the north–south (meridional) SST gradient enhances anomalous descent. The rising and sinking branches together help establish a cross-basin Walker circulation between the tropical western Atlantic and the eastern Pacific doi.org. This is the same kind of atmospheric loop that links the warm pool of the western Pacific with the cold eastern equatorial Pacific.

Model experiments

Once the cross-basin circulation is in place, the enhanced Pacific Walker circulation contributes to the development of La Niña, and the Atlantic Niño–ENSO connection strengthens doi.org. In the sensitivity experiments, the researchers modified the temperature gradients. The favorable configuration built up the cross-basin circulation, while the opposite configuration left the two oceans effectively decoupled doi.org.

The authors state that the study identifies new drivers of tropical Atlantic–Pacific linkages that are relevant to ENSO prediction doi.org. They note that future work should further quantify how the temperature gradients of each basin contribute to cross-basin interactions.

Yunnan University: Atlantic and Pacific SST gradients switch the Atlantic Niño–ENSO link on and off

Atlantic zonal and Pacific meridional gradients

Model experiments

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