Super La Niña in a Warming World

Extreme El Niño–Southern Oscillation (ENSO) events exert profound impacts on global climate and ecosystems. To date, the most extreme ENSO events on record have all been El Niño episodes whereas even the strongest La Niña events have been considerably weaker. In this talk, I show that the strongest El Niño may slightly weaken in the twenty-first century under future warming scenarios, whereas the strongest La Niña will intensify substantially. Specifically, unprecedentedly strong La Niña episodes—exceeding the strength of the strongest El Niño—are projected to emerge, which we term Super La Niña. Super La Niña is characterized by thermocline outcropping at its peak, an extreme oceanic state during which the easternmost thermocline nearly shoals to the surface. The emergence of Super La Niña and the associated thermocline outcropping are driven by intensified thermocline feedback, involving an amplified coupling between ocean cooling, atmospheric wind response, and thermocline tilt. These findings suggest that Super La Niña will emerge as one of the defining modes of future climate extremes, with intense and widespread teleconnection impacts on global surface temperature and precipitation.