Self-organized criticality in the El Niño Southern oscillation

The Fourier analysis has been applied to observational sea surface temperature (SST) data from the Southern Pacific. The spectral response of the daily temperature fluctuations indicates that the so-called El Niño Southern Oscillation (ENSO) belongs to the class of dynamical phenomena which are in a self-organized critical state. This has implications on the predictability of the significant events in the ocean-atmosphere interaction process. A toy model is used to point out the similarities of this system with other large scale phenomena, as earthquakes and volcanic eruptions, which are considered to be consistent with the hypothesis of self-organized criticality. The qualitative agreement between observational data and results of numerical simulations demonstrates the validity extent of the theoretical approach.