Abstract
The El Nino-Southern Oscillation (ENSO) is the dominant interannual variability of Earth’s climate system, and strongly modulates global temperature, precipitation, atmospheric circulation, tropical cyclones and other extreme events. However, forecasting ENSO is one of the most difficult problems in climate sciences affecting both interannual climate prediction and decadal prediction of near-term global climate change. The key question is what cause the switch between El Nino and La Nina. For the past 30 years, ENSO forecasts have been limited to short lead times after ENSO sea surface temperature (SST) anomaly has already developed, but unable to predict the switch between El Nino and La Nina. Here, we demonstrate that the switch between El Nino and La Nina is caused by a subsurface ocean wave propagating from western Pacific to central and eastern Pacific and then triggering development of SST anomaly. This is based on analysis of all ENSO events in the past 136 years using multiple long-term observational datasets. The wave’s slow phase speed and decoupling from atmosphere indicate that it is a forced wave. Further analysis of Earth’s angular momentum budget and NASA’s Apollo Landing Mirror Experiment suggests that the subsurface wave is likely driven by lunar tidal gravitational force.
Highlights
The existing El Nino-Southern Oscillation (ENSO) theories can be categorized into six groups[31,32,33] (Supplementary Fig. 3) including (1) slow coupled mode theories[3,34,35,36], (2) stochastic forcing theories[37,38], (3) recharge oscillator theory[39], (4) delayed oscillator theory[40,41,42], (5) advective-reflective oscillator theory[43], and (6) western Pacific oscillator theory[44]
Www.nature.com/scientificreports free Kelvin waves are generally 2–3 m/s, while those of the free Rossby waves are 0.5–1 m/s. These waves are driven by anomalous westerly or easterly winds[55], which are often associated with the intraseasonal Madden-Julian Oscillation (MJO)[56,57,58,59], and show clear horizontal and vertical propagations associated with different types of El Nino[60]
We demonstrate that the switch between El Nino and La Nina is caused by a subsurface ocean wave propagating from western Pacific to central/eastern Pacific, and trigger the development of sea surface temperature anomaly there
Summary
The existing ENSO theories can be categorized into six groups[31,32,33] (Supplementary Fig. 3) including (1) slow coupled mode theories[3,34,35,36], (2) stochastic forcing theories[37,38], (3) recharge oscillator theory[39], (4) delayed oscillator theory[40,41,42], (5) advective-reflective oscillator theory[43], and (6) western Pacific oscillator theory[44]. We demonstrate that the switch between El Nino and La Nina is caused by a subsurface ocean wave propagating from western Pacific to central/eastern Pacific, and trigger the development of sea surface temperature anomaly there.
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