The Atlantic Niño/Niña is a dominant mode of interannual variability peaking in boreal summer with substantial climate impacts. How the Atlantic Niño/Niña sea surface temperature (SST) variability may change under greenhouse warming remains unclear. Here we find a robust suppression in future Atlantic Niño/Niña variability in models that simulate a reasonable mean climatology of the equatorial Atlantic. Under greenhouse warming, the equatorial Atlantic atmosphere becomes more stable, reducing sensitivity of the equatorial zonal winds to the zonal SST gradient; further, weakened trade winds lead to a deepened thermocline in the east, reducing SST sensitivity to thermocline anomalies. These changes feed into Bjerknes feedback to cause suppression in Atlantic Niño/Niña SST variability. These findings are in stark contrast to the Pacific and the Indian Ocean where El Niño/La Niña SST variability and strong Indian Ocean Dipole variability are projected to increase.
The Atlantic Niño/Niña is an important mode of tropical climate variability, but how it changes with global warming is not clear. Here the authors use a comprehensive model ensemble to show that the Atlantic Niño/Niña system will probably weaken under greenhouse warming.