Changes in equatorial Pacific thermocline depth in response to Panamanian seaway closure: Insights from a multi-model study

TitleChanges in equatorial Pacific thermocline depth in response to Panamanian seaway closure: Insights from a multi-model study
Publication TypeJournal Article
Year of Publication2012
AuthorsZhang, X., M. Prange, S. Steph, M. Butzin, U. Krebs, D. J. Lunt, K. H. Nisancioglu, W. Park, A. Schmittner, B. Schneider, and M. Schulz
JournalEarth and Planetary Science Letters
Volume317
Pagination76-84
Date PublishedFeb 1
ISBN Number0012-821X
Accession NumberISI:000301616700008
Keywordscentral-american seaway, climate model, climate modeling, eastern tropical pacific, equatorial pacific, glaciation, meridional overturning circulation, north-atlantic, ocean circulation, panama closure, permanent el-nino, pliocene, pliocene warm period, tropical thermocline, water circulation
Abstract

The early Pliocene warm phase was characterized by high sea surface temperatures and a deep thermocline in the eastern equatorial Pacific. A new hypothesis suggests that the progressive closure of the Panamanian seaway contributed substantially to the termination of this zonally symmetric state in the equatorial Pacific. According to this hypothesis, intensification of the Atlantic meridional overturning circulation (AMOC) - induced by the closure of the gateway - was the principal cause of equatorial Pacific thermocline shoaling during the Pliocene. In this study, twelve Panama seaway sensitivity experiments from eight ocean/climate models of different complexity are analyzed to examine the effect of an open gateway on AMOC strength and thermocline depth. All models show an eastward Panamanian net throughflow, leading to a reduction in AMOC strength compared to the corresponding closed-Panama case. In those models that do not include a dynamic atmosphere, deepening of the equatorial Pacific thermocline appears to scale almost linearly with the throughflow-induced reduction in AMOC strength. Models with dynamic atmosphere do not follow this simple relation. There are indications that in four out of five models equatorial wind-stress anomalies amplify the tropical Pacific thermocline deepening. In summary, the models provide strong support for the hypothesized relationship between Panama closure and equatorial Pacific thermocline shoaling. (C) 2011 Elsevier B.V. All rights reserved.

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