Explaining away El Niño Modoki
The traditional view of El Niño is that it starts with a warm sea surface anomaly off the west coast of South America. This aberrant warming drifts west from the coast, triggering peak sea surface temperatures in the central Pacific during the southern summer. However, as the observational record grows and the full range of variability comes into view, some researchers have suggested that a recent slate of El Niño events that focus on the central Pacific, skipping the eastern warming, is indicative of the system being composed of at least two unique climate dynamics. The central Pacific–focused El Niño Modoki has been increasing in prevalence over recent decades, and researchers expect this trend to continue with global warming. New research by Takahashi et al., (2011) however, indicates that El Niño Modoki and the classical type are, in fact, one but that the perceived divergent behavior highlights the dynamic range of the system. Using El Niño observations stretching back to 1870, the authors perform a statistical analysis, breaking down the data set to isolate hidden spatial and temporal patterns. The Modoki and traditional El Niño records did not show the clustering that would be expected for separate climate phenomena. What did stand out, however, were the extreme warm events that occurred in the eastern Pacific in 1982–1983 and 1997–1998. On the basis of their findings, the authors propose two indices to describe the development of El Niño events: one for the moderate warming of the central Pacific and another for the extreme heat sometimes seen in the east. Therefore, the propagation of a given El Niño would be a combination of these two variables.
Published: 27 May 2011
Citation: (2011), ENSO regimes: Reinterpreting the canonical and Modoki El Niño, Geophys. Res. Lett., 38, L10704, doi:10.1029/2011GL047364.