ICES Journal of Marine Science: Journal du Conseil Advance Access originally published online on March 28, 2009
ICES Journal of Marine Science: Journal du Conseil 2009 66(7):1439-1447; doi:10.1093/icesjms/fsp061
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This article appears in the following ICES Journal of Marine Science issue: Effects of Climate Change on the World's Oceans [View the issue table of contents]
Sensitivity of thermohaline circulation to decadal and multidecadal variability
1 Faculty of Sciences, Campus de Ourense, University of Vigo, Spain
2 MeteoGalicia, Consellería de Medio Ambiente-Xunta de Galicia, Santiago de Compostela, Spain
Correspondence to M. N. Lorenzo: tel: +34 988387329; fax: +34 988387227; e-mail: nlorenzo{at}uvigo.es
Lorenzo, M. N., Taboada, J. J., and Iglesias, I. 2009. Sensitivity of thermohaline circulation to decadal and multidecadal variability. – ICES Journal of Marine Science, 66: 1439–1447.In this paper, stochastic freshwater inputs with different variabilities are introduced into an Earth Model of Intermediate Complexity to study their effect on the behaviour of the thermohaline circulation (THC). The variability in the stochastic signal was set to be either decadal or multidecadal (70 years), based on intensity modulation of the El Niño-Southern Oscillation (ENSO) phenomenon. The results demonstrate a weakening of the THC in both the decadal and the multidecadal cases. This weakening results in a reduction in air surface temperature, mainly in the North Atlantic. Moreover, the 500-mb stream function also weakens. This causes lower rainfall in Western Europe, except in the areas most influenced by the Gulf Stream. Sea surface temperature is reduced significantly in the area around Greenland, whereas sea surface salinity is reduced around Greenland and in the Gulf Stream, but increased in the Labrador Sea and in Hudson Strait. The latter effects are more marked in the case where the variability of the inputs is multidecadal. The main implication of these results is that the natural decadal or multidecadal variability in freshwater inputs could have noticeable effects on the fate of the THC, which may be superimposed on the effects of climate change.
Keywords: abrupt climate change, decadal and multidecadal variability, stochastic forcing, thermohaline circulation
Received 15 August 2008; accepted 14 February 2009; advance access publication 28 March 2009.