Decadal oscillations in a simplified coupled model due to unstable interactions between zonal winds and ocean gyres

Type Article
Date 2003-12
Language English
Author(s) Arzel Olivier, Huck Thierry
Affiliation(s) Univ Bretagne Occidentale, UFR Sci F302, IFREMER, CNRS,UMR 6523,Lab Phys Oceans, F-29285 Brest, France.
Source Dynamics of Atmospheres and Oceans (0377-0265) (Elsevier), 2003-12 , Vol. 37 , N. 3 , P. 245-270
DOI 10.1016/j.dynatmoce.2003.08.001
WOS© Times Cited 6
Keyword(s) Ocean atmosphere system, Air sea interaction, Air sea coupling, Ocean circulation
Abstract A simplified coupled ocean-atmosphere 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 boundary 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 amplification 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 anomalous heat transport: it accounts for the scale selection, the growth and the southward propagation of sea surface temperature anomalies in the subtropical gyre. The latter is not only due to the slow advection by the mean current, but to a prevailing mechanism of self-advecting coupled oceanic and atmospheric waves, out of phase in latitude. Relevance to the observational record is discussed.
Full Text
File Pages Size Access
publication-647.pdf 45 510 KB Open access
Top of the page