El Niño–Southern Oscillation, Pliocene climate and equifinality

Bonham, Sarah G.; Haywood, Alan M.; Lunt, Daniel J.; Collins, Mathew; Salzmann, Ulrich. 2009 El Niño–Southern Oscillation, Pliocene climate and equifinality. Philosophical Transactions of the Royal Society of London, A, 367 (1886). 127-156.

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It has been suggested that, during the Pliocene (ca 5–1.8Ma), an El Niño state existed as a permanent rather than an intermittent feature; that is, the tropical Pacific Ocean was characterized by a much weaker east–west gradient than today. One line of inquiry used to investigate this idea relates modern El Niño teleconnections to Pliocene proxy data by comparing regional differences in precipitation and surface temperature with climate patterns associated with present-day El Niño events, assuming that agreement between Pliocene data and observations of modern El Niño events supports this interpretation. Here, we examine this assumption by comparing outputs from a suite of Mid-Pliocene climate simulations carried out with the UK Met Office climate model. Regional patterns of climate change associated with changes in model boundary conditions are compared with observed El Niño–Southern Oscillation teleconnection patterns. Our results indicate that many of the proposed ‘permanent El Niño’ surface temperature and precipitation patterns are observable in Mid-Pliocene climate simulations even when they display variability in tropical Pacific sea surface temperatures (SSTs) or when forced with a modern east–west SST gradient. Our experiments highlight the possibility that the same outcome may be achieved through different initial conditions (equifinality); an important consideration for reconstructed patterns of regional Mid-Pliocene climate.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: BAS Programmes > Global Science in the Antarctic Context (2005-2009) > Greenhouse to Icehouse. Evolution of the Antarctic Cryosphere and Palaeoenvironment
ISSN: 1364-503X
Additional Keywords: Pliocene, El Niño, El Niño–Southern Oscillation, teleconnections, climate models, equifinality
NORA Subject Terms: Ecology and Environment
Earth Sciences
Date made live: 05 Feb 2009 10:27 +0 (UTC)

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