Cross-equatorial winds control El Niño diversity and change


Over the past two decades, El Niño events have weakened on average and their sea surface temperature (SST) anomalies shifted westward towards the central Pacific. Moreover, the intertropical convergence zone (ITCZ), which typically migrates southward from its northerly position during El Niño events, has not crossed the Equator since 1998. The causes of these changes remain under debate1,2,3,4,5. Here, using in situ, satellite and atmospheric reanalysis data, we show they can be related to a multidecadal strengthening of cross-equatorial winds in the eastern Pacific. This gradual strengthening of meridional winds is unlikely to be caused by El Niño/Southern Oscillation (ENSO) changes, and contains signals forced both locally and from outside the tropical Pacific, probably from the tropical North Atlantic. Coupled model simulations in which the observed cross-equatorial wind strengthening is superimposed successfully reproduce the key features of the recent changes in tropical climate. In particular, the tropical mean state experiences a ‘La Niña-like’ change, the ENSO amplitude weakens by about 20%, the centre of the SST anomalies shifts westward and the ITCZ now rarely crosses the Equator. Thus, cross-equatorial winds are found to modulate tropical Pacific mean state and variability, with implications for quantifying projected changes in ENSO under anthropogenic warming.

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Fig. 1: Observed multidecadal changes in tropical Pacific mean state and ENSO.
Fig. 2: Observed trends and variations in cross-equatorial winds.
Fig. 3: Coupled model response to the superimposed cross-equatorial wind anomaly.
Fig. 4: Cross-equatorial winds and their projected changes (RCP8.5 (2066–2095) minus historical (1971–2000)) in CMIP5 models.


  1. 1.

    Ashok, K., Behera, S. K., Rao, S. A., Weng, H. Y. & Yamagata, T. El Niño Modoki and its possible teleconnection. J. Geophys. Res. Oceans 112, C11007 (2007).

    Article  Google Scholar 

  2. 2.

    Kao, H. Y. & Yu, J. Y. Contrasting eastern-Pacific and central-Pacific types of ENSO. J. Clim. 22, 615–632 (2009).

    Article  Google Scholar 

  3. 3.

    Kug, J. S., Jin, F. F. & An, S. I. Two types of El Niño events: cold tongue El Niño and warm pool El Niño. J. Clim. 22, 1499–1515 (2009).

    Article  Google Scholar 

  4. 4.

    Yeh, S. W. et al. El Niño in a changing climate. Nature 461, 511–514 (2009).

    Article  CAS  Google Scholar 

  5. 5.

    McPhaden, M. J., Lee, T. & McClurg, D. El Niño and its relationship to changing background conditions in the tropical Pacific Ocean. Geophys. Res. Lett. 38, L15709 (2011).

    Article  Google Scholar 

  6. 6.

    Fedorov, A. V. & Philander, S. G. Is El Niño changing? Science 288, 1997–2002 (2000).

    Article  CAS  Google Scholar 

  7. 7.

    McPhaden, M. J., Zebiak, S. E. & Glantz, M. H. ENSO as an integrating concept in Earth science. Science 314, 1740–1745 (2006).

    Article  CAS  Google Scholar 

  8. 8.

    Collins, M. et al. The impact of global warming on the tropical Pacific Ocean and El Niño. Nat. Geosci. 3, 391–397 (2010).

    Article  CAS  Google Scholar 

  9. 9.

    Cai, W. et al. Increasing frequency of extreme El Niño events due to greenhouse warming. Nat. Clim. Change 4, 111–116 (2014).

    Article  CAS  Google Scholar 

  10. 10.

    Cai, W. et al. ENSO and greenhouse warming. Nat. Clim. Change 5, 849–859 (2015).

    Article  Google Scholar 

  11. 11.

    Capotondi, A. & Sardeshmukh, P. D. Is El Niño really changing? Geophys. Res. Lett. 44, 8548–8556 (2017).

    Article  Google Scholar 

  12. 12.

    Yeh, S. W. et al. ENSO atmospheric teleconnections and their response to greenhouse gas forcing. Rev. Geophys. 56, 185–206 (2018).

    Article  Google Scholar 

  13. 13.

    Hu, S. & Fedorov, A. V. Exceptionally strong easterly wind burst stalling El Niño of 2014. Proc. Natl Acad. Sci. USA 113, 2005–2010 (2016).

    Article  CAS  Google Scholar 

  14. 14.

    Levine, A. F. Z. & McPhaden, M. J. How the July 2014 easterly wind burst gave the 2015–2016 El Niño a head start. Geophys. Res. Lett. 43, 6503–6510 (2016).

    Article  Google Scholar 

  15. 15.

    Hu, S. & Fedorov, A. V. The extreme El Niño of 2015–2016: the role of westerly and easterly wind bursts, and preconditioning by the failed 2014 event. Clim. Dynam. (2017).

  16. 16.

    Puy, M. et al. Influence of westerly wind events stochasticity on El Niño amplitude: the case of 2014 vs. 2015. Clim. Dynam. (2017).

  17. 17.

    Santoso, A., McPhaden, M. J. & Cai, W. The defining characteristics of ENSO extremes and the strong 2015/16 El Niño. Rev. Geophys. 55, 1079–1129 (2017).

    Article  Google Scholar 

  18. 18.

    England, M. H. et al. Recent intensification of wind-driven circulation in the Pacific and the ongoing warming hiatus. Nat. Clim. Change 4, 222–227 (2014).

    Article  Google Scholar 

  19. 19.

    Capotondi, A. et al. Understanding ENSO Diversity. Bull. Am. Meteorol. Soc. 96, 921–938 (2015).

    Article  Google Scholar 

  20. 20.

    Wittenberg, A. T. Are historical records sufficient to constrain ENSO simulations? Geophys. Res. Lett. 36, L12702 (2009).

    Article  Google Scholar 

  21. 21.

    Xie, S. P. & Philander, S. G. H. A coupled ocean-atmosphere model of relevance to the ITCZ in the Eastern Pacific. Tellus A 46, 340–350 (1994).

    Article  Google Scholar 

  22. 22.

    Li, X., Xie, S. P., Gille, S. T. & Yoo, C. Atlantic-induced pan-tropical climate change over the past three decades. Nat. Clim. Change 6, 275–279 (2016).

    Article  Google Scholar 

  23. 23.

    Enfield, D. B., Mestas‐Nuñez, A. M. & Trimble, P. J. The Atlantic multidecadal oscillation and its relation to rainfall and river flows in the continental US. Geophys. Res. Lett. 28, 2077–2080 (2001).

    Article  Google Scholar 

  24. 24.

    Chiang, J. C. H. & Friedman, A. R. Extratropical cooling, interhemispheric thermal gradients, and tropical climate change. Ann. Rev. Earth Planet. Sci. 40, 383–412 (2012).

    Article  CAS  Google Scholar 

  25. 25.

    Frierson, D. M. & Hwang, Y. T. Extratropical influence on ITCZ shifts in slab ocean simulations of global warming. J. Clim. 25, 720–733 (2012).

    Article  Google Scholar 

  26. 26.

    Li, G. & Xie, S. P. Tropical biases in CMIP5 multimodel ensemble: the excessive equatorial Pacific cold tongue and double ITCZ problems. J. Clim. 27, 1765–1780 (2014).

    Article  Google Scholar 

  27. 27.

    Philander, S. G. H. & Pacanowski, R. C. The oceanic response to cross-equatorial winds (with application to coastal upwelling in low latitudes). Tellus 33, 201–210 (1981).

    Article  Google Scholar 

  28. 28.

    Lübbecke, J. F. & McPhaden, M. J. Assessing the twenty-first-century shift in ENSO variability in terms of the Bjerknes stability index. J. Clim. 27, 2577–2587 (2014).

    Article  Google Scholar 

  29. 29.

    Timmermann, A. et al. The influence of a weakening of the Atlantic meridional overturning circulation on ENSO. J. Clim. 20, 4899–4919 (2007).

    Article  Google Scholar 

  30. 30.

    Levine, A. F., McPhaden, M. J. & Frierson, D. M. The impact of the AMO on multidecadal ENSO variability. Geophys. Res. Lett. 44, 3877–3886 (2017).

    Article  Google Scholar 

  31. 31.

    Cheng, W., Chiang, J. C. H. & Zhang, D. X. Atlantic Meridional Overturning Circulation (AMOC) in CMIP5 Models: RCP and historical simulations. J. Clim. 26, 7187–7197 (2013).

    Article  Google Scholar 

  32. 32.

    Rahmstorf, S. et al. Exceptional twentieth-century slowdown in Atlantic Ocean overturning circulation. Nat. Clim. Change 5, 475–480 (2015).

    Article  Google Scholar 

  33. 33.

    Sevellec, F., Fedorov, A. V. & Liu, W. Arctic sea-ice decline weakens the Atlantic Meridional Overturning Circulation. Nat. Clim. Change 7, 604–610 (2017).

    Article  Google Scholar 

  34. 34.

    Xie, S. P. et al. Global warming pattern formation: sea surface temperature and rainfall. J. Clim. 23, 966–986 (2010).

    Article  Google Scholar 

  35. 35.

    Wang, H., Xie, S. P., Tokinaga, H., Liu, Q. & Kosaka, Y. Detecting cross-equatorial wind change as a fingerprint of climate response to anthropogenic aerosol forcing. Geophys. Res. Lett. 43, 3444–3450 (2016).

    Article  Google Scholar 

  36. 36.

    Giese, B. S. & Ray, S. El Niño variability in simple ocean data assimilation (SODA), 1871–2008. J. Geophys. Res. Oceans 116, C02024 (2011).

    Article  Google Scholar 

  37. 37.

    Fedorov, A. V., Hu, S. N., Lengaigne, M. & Guilyardi, E. The impact of westerly wind bursts and ocean initial state on the development, and diversity of El Niño events. Clim. Dynam. 44, 1381–1401 (2015).

    Article  Google Scholar 

  38. 38.

    Deser, C. et al. ENSO and Pacific decadal variability in the Community Climate System Model Version 4. J. Clim. 25, 2622–2651 (2012).

    Article  Google Scholar 

  39. 39.

    Capotondi, A. ENSO diversity in the NCAR CCSM4 climate model. J. Geophys. Res. Oceans 118, 4755–4770 (2013).

    Article  Google Scholar 

  40. 40.

    Manabe, S. & Stouffer, R. J. Two stable equilibria of a coupled ocean–atmosphere model. J. Clim. 1, 841–866 (1988).

    Article  Google Scholar 

  41. 41.

    Liu, W., Liu, Z. Y. & Brady, E. C. Why is the AMOC monostable in coupled general circulation models? J. Clim. 27, 2427–2443 (2014).

    Article  Google Scholar 

  42. 42.

    Vega-Westhoff, B. & Sriver, R. L. Analysis of ENSO’s response to unforced variability and anthropogenic forcing using CESM. Sci. Rep. 7, 18047 (2017).

    Article  CAS  Google Scholar 

  43. 43.

    Taylor, K. E., Stouffer, R. J. & Meehl, G. A. An overview of CMIP5 and the experiment design. Bull. Am. Meteorol. Soc. 93, 485–498 (2012).

    Article  Google Scholar 

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This research was supported by grants to A.V.F. from the NSF (AGS- 0163807) and NASA (NNX17AH21G). S.H. was supported by a NASA Earth and Space Sciences Graduate Fellowship, and a Scripps Institutional Postdoctoral Fellowship. We also acknowledge computational support from the Yale University Faculty of Arts and Sciences High Performance Computing facility and from the NSF/NCAR Yellowstone Supercomputing Center.

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S.H. and A.V.F. contributed equally to designing the research and writing the manuscript. S.H. performed the data analysis and numerical simulations and, together with A.V.F., interpreted the results.

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Correspondence to Shineng Hu.

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Hu, S., Fedorov, A.V. Cross-equatorial winds control El Niño diversity and change. Nature Clim Change 8, 798–802 (2018).

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