Climate Fact: Holocene ENSO Variability
Variations in the temperature distribution gradient in the tropical Pacific (characterized by the state of the El Niño-Southern Oscillation (ENSO), the oscillation in the eastern tropical Pacific between cool (La Niña) and warm (El Niño) states) exerts a strong influence on upper-atmospheric circulation and affects weather throughout the world. Surface temperature distributions in the tropical Pacific are sensitive to variations in solar intensity and even slight changes in solar or volcanic activity can have marked effects on the tropical Pacific and Earth’s climate. ENSO’s properties are also strongly influenced by the behavior of the Peru (Humboldt) Current, which moves from the north to south along the South American coast and is in turn influenced by variations in the Antarctic Circumpolar Current. During the early Holocene (12,000 years ago to about 5,400 years ago), the tropical Pacific had a strong temperature gradient between the east and west (i.e. it was in a semi-permanent La Niña state) and El Niño events were effectively suppressed. Between about 5,400 and 4,600 years ago, the variability between the two phases became more pronounced. Because short-term solar influences cannot explain this shift, it is likely that changes originating from the poles as a result of longer-term changes linked to the deglaciation are needed to explain the transition.
Seasons: Winter, Spring, Summer, Fall
Source: Chazen, CR et al. “Abrupt mid-Holocene onset of centennial-scale climate variability on the Peru-Chile Margin.” Geophysical Research Letters 35 (2009): L18704.