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The role of oceanic feedbacks in the 2014–2016 El Niño events as derived from ocean reanalysis data

Abstract

Why did the predicted “super El Niño” fade out in the summer 2014 and the following year develop into one of the three strongest El Niño on record? Although some hypotheses have been proposed in previous studies, the quantitative contribution of oceanic processes to these events remains unclear. We investigated the role of various oceanic feedbacks, especially in response to intra-seasonal westerly wind busts, in the evolution of the 2014–2016 El Niño events, through a detailed heat budget analysis using high temporal resolution Estimating the Circulation and Climate of the Ocean—Phase II (ECCO2) simulation outputs and satellite-based observations. Results show that the Ekman feedback and zonal advective feedback were the two dominant oceanic processes in the developing phase of the warm event in the spring of 2014 and its decay in June. In the 2015–2016 super El Niño event, the zonal advective feedback and thermocline feedback played a significant role in the eastern Pacific warming. Moreover, the thermocline feedback tended to weaken in the central Pacific where the zonal advection feedback became the dominant positive feedback.

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Acknowledgment

We thank Dr. Michael J. McPhaden of NOAA/Pacific Marine Environmental Laboratory for his valuable comments. We acknowledge NOAA and NASA JPL for their valuable observations and model products.

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Correspondence to Fan Wang.

Additional information

Supported by the National Natural Science Foundation of China (No. 41806016) and the China Postdoctoral Science Foundation (No. 2017M622289) to GUAN Cong; the National Natural Science Foundation of China (Nos. 41776018, 91858101) and the Strategic Priority Research Program of Chinese Academy of Sciences (No. XDB01000000) to HU Shijian; the State Key Program of National Natural Science of China (No.41730534) and The NSFC Innovative Group Grant (No. 41421005) to WANG Fan

Data Availability Statement

The OISSTv2 data are available at www.ncdc.noaa.gov, the SSH data are from the AVISO altimeter at www.aviso.altimetry.fr, the wind stress data from NOAA/ERDDAP are at https://coastwatch.pfeg.noaa.gov/erddap, and OSCAR surface ocean current at http://podaac.jpl.nasa.gov. The ECCO2 outputs can be found at ftp://ecco.jpl.nasa.gov/ECCO2.

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Guan, C., Wang, F. & Hu, S. The role of oceanic feedbacks in the 2014–2016 El Niño events as derived from ocean reanalysis data. J. Ocean. Limnol. 38, 1394–1407 (2020). https://doi.org/10.1007/s00343-020-0038-1

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Keyword

  • El Niño-Southern Oscillation (ENSO)
  • extreme El Niño
  • zonal advective feedback
  • thermocline feedback
  • Ekman feedback
  • inter-seasonal variability