Affiliation:
1. Institute of Geophysics and Meteorology University of Cologne Cologne Germany
2. GEOMAR Helmholtz Centre for Ocean Research Kiel Kiel Germany
3. Faculty of Mathematics and Natural Sciences Christian‐Albrechts‐University of Kiel Kiel Germany
Abstract
AbstractObserved El Niño‐Southern Oscillation (ENSO) varies between decades with high ENSO amplitude and more extreme Eastern Pacific (EP) El Niño events and decades with low ENSO amplitude and mainly weak El Niño events. Based on experiments with the CESM1 model, ENSO may lock‐in into an extreme EP El Niño‐dominated state in a +3.7 K warmer climate, while in a −4.0 K cooler climate ENSO may lock‐in into a weak El Niño‐dominated state. The state shift of ENSO with global warming can be explained by the location and amplitude of the strongest warming over the eastern equatorial Pacific, which amplifies the Bjerknes feedback and allows a southward migration of the Intertropical Convergence Zone onto the equator, a prerequisite of extreme EP El Niños. In light of these results, we discuss to what extent the state of ENSO may be a tipping element in the climate system.
Funder
Deutsche Forschungsgemeinschaft
Publisher
American Geophysical Union (AGU)