The unique 2009-2010 El Niño event: A fast phase transition of warm pool El Niño to La Niña

• Published in: Geophysical research letters Vol. 38; no. 15
• Main Authors: Kim, WonMoo, Yeh, Sang-Wook, Kim, Joo-Hong, Kug, Jong-Seong, Kwon, MinHo
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 01.08.2011; American Geophysical Union
• Subjects: Anomalies; Boundaries; Earth sciences; Earth, ocean, space; El Nino; El Niño; ENSO; Exact sciences and technology; Indian Ocean; Kelvin waves; La Nina; Phase transformations; Pools; transition; warm pool El Niño; Indian Ocean; Pacific Ocean; Central Pacific; I, Central Pacific; ISW, Indian Ocean; Kelvin wave; El Nino; upwelling; warming; phase transitions; Sea surface temperature; subsurface; anomalies; ocean circulation; La Nina
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2011GL048521

The latest El Niño event in 2009–2010, which is classified as warm pool El Niño, holds a unique ground in that it marks the strongest warming signal in the central Pacific but rapidly decays to strong La Niña. The strong eastward‐propagating cold anomaly at the subsurface level is found to be a key factor, and two possible mechanisms are suggested that resulted in the fast phase transition of the 2009–2010 event: 1) The anomalously warm Indian Ocean induces a surface easterly over the western edge of the Pacific, which generates the forced Kelvin waves. 2) The record‐breaking high sea surface temperature in the central Pacific excites a strong Rossby response that is to be reflected as an upwelling Kelvin wave at the western boundary. The strong subsurface anomaly then propagates eastward and results in an unusually fast phase transition of the 2009–2010 warm pool El Niño event. Key Points The 2009–2010 El Nino exhibits a unique evolution character (fast transition) The strong eastward‐propagating anomaly is found to be a key factor Warm Indian Ocean and strong central Pacific anomaly played active roles