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Effects of NAO variability on the North Atlantic Ocean circulation
Author(s) -
Bellucci A.,
Richards K. J.
Publication year - 2006
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2005gl024890
Subject(s) - ocean gyre , thermohaline circulation , climatology , forcing (mathematics) , north atlantic oscillation , empirical orthogonal functions , wind stress , atmospheric circulation , geology , atlantic multidecadal oscillation , ocean current , gulf stream , oceanography , ocean general circulation model , environmental science , atmospheric sciences , climate change , general circulation model , subtropics , fishery , biology
The ocean response to an idealised North Atlantic Oscillation‐like wind stress is evaluated as a function of the atmospheric forcing frequency. In order to elucidate the relationship between internal and forced variability, the NAO is modulated with two specific timescales, 10 and 50 years, which characterise the spectrum of the system's internal variability. Different timescales of atmospheric variability select distinct sea surface temperature (SST) and large scale circulation patterns. Under a 50 year NAO forcing period, a lagged SST response is excited in the Gulf Stream extension region, which is consistent with the spin‐up of the gyre circulation. The thermohaline circulation varies in phase with the NAO and shows a strong sensitivity to the forcing frequency: a dipole mode of the overturning is excited by a 10 year modulation of the NAO, while an enhanced overturning response emerges under a 50 year NAO. With low enough lateral mixing the ocean exhibits an irregular response to a regular NAO‐like forcing.