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Dynamics of Atmospheres and Oceans 37 (2003) 245270

Summary: Dynamics of Atmospheres and Oceans
37 (2003) 245­270
Decadal oscillations in a simplified coupled
model due to unstable interactions between
zonal winds and ocean gyres
Olivier Arzel, Thierry Huck
Laboratoire de Physique des Océans (UMR 6523 CNRS IFREMER UBO), Université de Bretagne Occidentale,
UFR Sciences F302, 6 avenue Le Gorgeu, B.P. 809, 29285 Brest, France
Received 1 May 2003; received in revised form 4 August 2003; accepted 28 August 2003
A simplified coupled ocean­atmosphere model, consisting of a one-layer bidimensional ocean
model and a one-layer unidimensional energy balance atmospheric model [J. Clim. 13 (2000) 232]
is used to study the unstable interactions between zonal winds and ocean gyres. In a specific range of
parameters, decadal variability is found. Anomalies, quite homogeneous zonally, show small-scale
wavelength in latitude: perturbations emerge and grow at the southern limb of the intergyre bound-
ary and propagate southward before decaying. The wind stress anomalies are proportional to the
meridional gradient of the atmospheric temperature anomalies: this ratio acts as a positive amplifica-
tion factor, as confirmed by a parameter sensitivity analysis. Assuming zonally-averaged anomalies
harmonic in the meridional direction, a very simple analytical model for the perturbations is derived,
based on forced Rossby wave adjustment of the western boundary current and its associated anoma-


Source: Arzel, Olivier - Climate Change Research Centre, University of New South Wales
Huck, Thierry - Laboratoire de Physique des Océans, Université de Bretagne Occidentale


Collections: Geosciences