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Eastern and Central Pacific ENSO and their relationships to the recharge/discharge oscillator paradigm

Singh, Awnesh M. and Delcroix, T. (2013) Eastern and Central Pacific ENSO and their relationships to the recharge/discharge oscillator paradigm. Deep Sea Research Part I: Oceanographic Research Papers, 82 . pp. 32-43. ISSN 0967-0637

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One of the leading theories to explain the oscillatory nature of ENSO is the recharge-discharge paradigm, which roots on warm waters exchanged between the equatorial and off-equatorial regions. This study tests the relevance of this theory to account for the Eastern and recently mediated Central Pacific El Niño events. The recharge-discharge of the equatorial Pacific, measured here as changes in Warm (>20°C) Water Volume (WWV), is analysed using monthly 1993-2010 sea level anomaly (a proxy for WWV) obtained from altimetry, and a validated 1958-2007 DRAKKAR simulation. An Agglomerative Hierarchical Clustering (AHC) technique performed on the observed and modelled WWV shows the existence of five distinct clusters, which characterize the Eastern Pacific (EP) and Central Pacific (CP) El Niño, La Niña, after EP El Niño and neutral conditions. The AHC results, complemented with an analysis of 3-month composites of typical EP and CP El Niño events, indicate that the equatorial band WWV discharge during CP is not as pronounced as during EP El Niño. To understand the differences, we analyze the balance of horizontal mass transport accounting for changes in WWV. The analysis indicates an overall poleward transport during EP El Niño, which is not the case during CP El Niño. Instead, a compensating effect with a poleward (equatorward) transport occurring in the western (eastern) Pacific is evident, in line with changes in the zonal thermocline slopes. The WWW changes are discussed with respect to the conceptual phases of the recharge-discharge oscillator paradigm.

Item Type: Journal Article
Subjects: Q Science > Q Science (General)
Q Science > QC Physics
Divisions: Pacific Centre for Environment and Sustainable Development (PACE-SD)
Depositing User: Awnesh Singh
Date Deposited: 02 Sep 2013 04:01
Last Modified: 06 Jul 2016 23:38

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