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Is ENSO a cycle or a series of events?
Author(s) -
Kessler William S.
Publication year - 2002
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2002gl015924
Subject(s) - el niño southern oscillation , climatology , amplitude , southern oscillation , annual cycle , impulse (physics) , series (stratigraphy) , oscillation (cell signaling) , persistence (discontinuity) , la niña , environmental science , geology , physics , chemistry , biochemistry , geotechnical engineering , quantum mechanics , paleontology
After early ideas that saw El Niños as isolated events, the advent of coupled models brought the conception of ENSO as a cycle in which each phase led to the next in a self‐sustained oscillation. Twenty‐two years of observations that represent the El Niño and La Niña peaks (east Pacific SST) and the memory of the system (zonal mean warm water volume) suggest a distinct break in the cycle, in which the coupled system is able to remain in a weak La Niña state for up to two years, so that memory of previous influences would be lost. Similarly, while the amplitude of anomalies persists from the onset of a warm event through its termination, there is no such persistence across the La Niña break. These observations suggest that El Niños are in fact event‐like disturbances to a stable basic state, requiring an initiating impulse not contained in the dynamics of the cycle itself.