Coupled ocean-atmosphere dynamics of the 2017 extreme coastal El Niño

• Published in: Nature communications Vol. 10; no. 1; p. 298
• Main Authors: Peng, Qihua, Xie, Shang-Ping, Wang, Dongxiao, Zheng, Xiao-Tong, Zhang, Hong
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 17-01-2019; Nature Publishing Group; Nature Portfolio
• Subjects: 704/106/35; 704/106/829/2737; Atmospheric models; Climate change; Climate models; Coastal environments; Coastal processes; Convection; El Nino; Global warming; Humanities and Social Sciences; Kelvin waves; La Nina; multidisciplinary; Ocean currents; Ocean models; Positive feedback; Prediction models; Rainfall; Science; Science (multidisciplinary); Sea surface temperature; Peru
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-018-08258-8

In March 2017, sea surface temperatures off Peru rose above 28 °C, causing torrential rains that affected the lives of millions of people. This coastal warming is highly unusual in that it took place with a weak La Niña state. Observations and ocean model experiments show that the downwelling Kelvin waves caused by strong westerly wind events over the equatorial Pacific, together with anomalous northerly coastal winds, are important. Atmospheric model experiments further show the anomalous coastal winds are forced by the coastal warming. Taken together, these results indicate a positive feedback off Peru between the coastal warming, atmospheric deep convection, and the coastal winds. These coupled processes provide predictability. Indeed, initialized on as early as 1 February 2017, seasonal prediction models captured the extreme rainfall event. Climate model projections indicate that the frequency of extreme coastal El Niño will increase under global warming.
The extreme coastal El Niño of March 2017 caused devastating flooding in coastal Peru but its mechanism remains unclear. Here the authors investigate the physical processes using observations and model simulations and suggest that such extreme coastal flooding is predictable and will become more frequent as climate warms.