The role of the Meridional Mode in ENSO diversity under greenhouse forcing

Giovanni Liguori, Georgia Institute of Technology Main Campus, Atlanta, GA, United States and Emanuele Di Lorenzo, Georgia Institute of Technology Main Campus, Program in Ocean Science & Engineering, Atlanta, GA, United States
Abstract:
The Pacific Meridional Mode (MM) is a coupled ocean-atmosphere mode of variability that is recognized as an important precursor of El Niño Southern Oscillation (ENSO) and its different flavors, the Eastern and Central Pacific. Recent study suggests that the coupling between the MM and ENSO is increasing under greenhouse forcing. Using 30 simulations with the Community Earth System Model at 1° spatial resolution over the period 1920-2100 (CESM1 Large Ensemble) we explore the dynamics controlling the MM activity and its coupling to ENSO diversity under a greenhouse forcing scenario. The CESM1 Large Ensemble shows that the equatorial variance increases significantly under greenhouse forcing, with a tendency for frequent large-amplitude (>2C anomalies) El Niño events in the central tropical Pacific. We show that these changes in ENSO statistics are linked to the changing character of the MM under greenhouse forcing.
Back to: El Niño–Southern Oscillation (ENSO) Diversity in a Changing Climate II