Abstract
The non-stationarity of the North Atlantic atmosphere-ocean coupling is investigated utilizing a long time integration of a coupled atmosphere-ocean general circulation model (GCM) and a consistent atmospheric experiment forced by the climatological sea surface temperature (SST) of the coupled GCM. The temporal behavior of the North Atlantic Oscillation (NAO) is non-stationary with two different decadal regimes being identified: (a) phases with enhanced (active) low-frequency variability of the NAO index are characterized by regional modes with a baroclinic Pacific-North America (PNA) and a dominant barotropic North Atlantic pattern; (b) in phases with reduced (passive) low-frequency variability a global mode connects tropics and midlatitudes. The characteristic space scales are similar in the coupled and the consistent atmospheric experiment; the time scales of the atmospheric eigenmodes are modified by ocean dynamics. In the active (passive) phase the corresponding atmospheric mode is reinforced by the North Atlantic (tropical Pacific) SST.
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Received: 15 September 2000 / Accepted: 30 March 2001
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Raible, C., Luksch, U., Fraedrich, K. et al. North Atlantic decadal regimes in a coupled GCM simulation. Climate Dynamics 18, 321–330 (2001). https://doi.org/10.1007/s003820100176
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DOI: https://doi.org/10.1007/s003820100176