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contributor authorDong, Buwen
contributor authorSutton, Rowan T.
date accessioned2017-06-09T17:03:37Z
date available2017-06-09T17:03:37Z
date copyright2007/10/01
date issued2007
identifier issn0894-8755
identifier otherams-78745.pdf
identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4221448
description abstractA coupled ocean?atmosphere general circulation model is used to investigate the modulation of El Niño?Southern Oscillation (ENSO) variability due to a weakened Atlantic thermohaline circulation (THC). The THC weakening is induced by freshwater perturbations in the North Atlantic, and leads to a well-known sea surface temperature dipole and a southward shift of the intertropical convergence zone (ITCZ) in the tropical Atlantic. Through atmospheric teleconnections and local coupled air?sea feedbacks, a meridionally asymmetric mean state change is generated in the eastern equatorial Pacific, corresponding to a weakened annual cycle, and westerly anomalies develop over the central Pacific. The westerly anomalies are associated with anomalous warming of SST, causing an eastward extension of the west Pacific warm pool particularly in August?February, and enhanced precipitation. These and other changes in the mean state lead in turn to an eastward shift of the zonal wind anomalies associated with El Niño events, and a significant increase in ENSO variability. In response to a 1-Sv (1 Sv ≡ 106 m3 s?1) freshwater input in the North Atlantic, the THC slows down rapidly and it weakens by 86% over years 50?100. The Niño-3 index standard deviation increases by 36% during the first 100-yr simulation relative to the control simulation. Further analysis indicates that the weakened THC not only leads to a stronger ENSO variability, but also leads to a stronger asymmetry between El Niño and La Niña events. This study suggests a role for an atmospheric bridge that rapidly conveys the influence of the Atlantic Ocean to the tropical Pacific and indicates that fluctuations of the THC can mediate not only mean climate globally but also modulate interannual variability. The results may contribute to understanding both the multidecadal variability of ENSO activity during the twentieth century and longer time-scale variability of ENSO, as suggested by some paleoclimate records.
publisherAmerican Meteorological Society
titleEnhancement of ENSO Variability by a Weakened Atlantic Thermohaline Circulation in a Coupled GCM
typeJournal Paper
journal volume20
journal issue19
journal titleJournal of Climate
identifier doi10.1175/JCLI4284.1
journal fristpage4920
journal lastpage4939
treeJournal of Climate:;2007:;volume( 020 ):;issue: 019
contenttypeFulltext


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