Contrasting the flavors of ENSO and related trends in the tropical Pacific Ocean in recent decades

Abstract

The main features of the Eastern (EP) and Central (CP) Pacific El Niño Southern Oscillation (ENSO) events are analyzed using 1950-2010 observed and modeled data. Using various analysis techniques, we found that the CP El Niño differs from the canonical EP El Niño in terms of amplitude and location of maximum/minimum sea surface temperature, sea surfacesalinity and sea level anomalies, and the recharge/discharge (R/D) dynamical mode. The distinctive R/D features are characterized by different transport mechanisms: during EP El Niño, there is a mass discharge of warm waters (>20°C) over the entire equatorial band resulting in a change from El Niño to La Niña conditions. Whereas during CP El Niño, there is a compensating effect ensuing in relatively no overall discharge. Furthermore, the longterm trends due to ENSO are mostly because of the influence of CP El Niño, which for example, accounts up to 30% of the warming/freshening trends in the western-central equatorial Pacific