Publication Date:
2017-07-27
Description:
The El Niño–Southern Oscillation (ENSO) non-linear oscillator phenomenon has a far reaching influence on the climate and human activities. The upto 10 year quasi-period cycle of the El Niño and subsequent La Niña is known to be dominated in the tropics by non-linear physical interaction of wind with the equatorial wave-guide in the Pacific. Long term cyclic phenomena do not feature in the current theory of the ENSO process. We update the theory by assessing low (〉 10 years) and high (〈 10 years) frequency coupling using evidence across tropical, extratropical and Pacific basin scales. We analyse observations and model simulations with a highly accurate method called Dominant Frequency State Analysis (DFSA) to provide evidence of stable ENSO features. The observational datasets of the Southern Oscillation Index (SOI), North Pacific Index Anomaly and ENSO Sea Surface Temperature Anomaly, as well as a theoretical model all confirm the existence of long and short term climatic cycles of the ENSO process with resonance frequencies of {2.5, 3.8, 5, 12 to 14, 61 to 75, 180} years. This fundamental result shows long and short term signal coupling with mode locking across the dominant ENSO dynamics. These dominant oscillation frequency dynamics, defined as ENSO frequency states, contain a stable attractor with three frequencies in resonance allowing us to coin the term Heartbeat of the Southern Oscillation due to its characteristic shape. We predict future ENSO states based on a stable hysteresis scenario of short and long term ENSO oscillations over the next century.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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