Letter | Published:

All flavours of El Niño have similar early subsurface origins

Nature Climate Change volume 3, pages 4246 (2013) | Download Citation


The El Niño/Southern Oscillation phenomenon, characterized by anomalous sea surface temperatures and winds in the tropical Pacific, affects climate across the globe1. El Niños occur every 2–7 years, whereas the El Niño/Southern Oscillation itself varies on decadal timescales in frequency and amplitude, with a different spatial pattern of surface anomalies2 each time the tropical Pacific undergoes a regime shift. Recent work has shown that Bjerknes feedback3,4 (coupling of the atmosphere and the ocean through changes in equatorial winds driven by changes in sea surface temperature owing to suppression of equatorial upwelling in the east Pacific) is not necessary5 for the development of an El Niño. Thus it is unclear what remains constant through regimes and is crucial for producing the anomalies recognized as El Niño. Here we show that the subsurface process of discharging warm waters always begins in the boreal summer/autumn of the year before the event (up to 18 months before the peak) independent of regimes, identifying the discharge process as fundamental to the El Niño onset. It is therefore imperative that models capture this process accurately to further our theoretical understanding, improve forecasts and predict how the El Niño/Southern Oscillation may respond to climate change.

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This work was carried out at the Divecha Centre for Climate Change, Indian Institute of Science, Bangalore—560012, India, enabled by grants from the same. The authors would like to thank J. Beauchamp for providing the SODA, Global Ocean Data Assimilation System and Global High-Resolution SST data. N.R. would like to thank S. R. Parampil for assistance with the Ferret software.

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  1. Divecha Centre for Climate Change, Indian Institute of Science, Bangalore 560012, India

    • Nandini Ramesh
  2. Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20742, USA

    • Raghu Murtugudde


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Analysis of the data, production of the figures and writing of the final manuscript was carried out by N.R. The project was supervised and directed by R.M. who interpreted results and also edited the final manuscript.

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The authors declare no competing financial interests.

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Correspondence to Nandini Ramesh.

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