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GEOPHYSICAL RESEARCH LETTERS, VOL. 31, L09210, doi:10.1029/2004GL019548, 2004

Causes of low frequency North Atlantic SST variability in a coupled GCM

Zhaohua Wu

Center for Ocean-Land-Atmosphere Studies, Calverton, Maryland, USA


E. K. Schneider

Center for Ocean-Land-Atmosphere Studies, Calverton, Maryland, USA
Program in Climate Dynamics, School of Computational Sciences, George Mason University, Fairfax, Virginia, USA


B. P. Kirtman

Center for Ocean-Land-Atmosphere Studies, Calverton, Maryland, USA
Program in Climate Dynamics, School of Computational Sciences, George Mason University, Fairfax, Virginia, USA


Abstract

The relative roles of stable and unstable coupled feedbacks in inducing the low frequency SST variability in various regions of the North Atlantic are studied using a coupled general circulation model. The interactive ensemble technique is applied to reduce the strength of “weather noise” in the model and isolate the atmospheric feedback to boundary forcing. We find that the low frequency SST variability in the subtropical North Atlantic is mainly induced by stable coupled feedbacks in which the weather noise plays a central role. However, in the Gulf Stream extension area, the SST variability may be attributed to processes internal to the ocean. Although the results are not definitive, there is no compelling evidence that unstable coupled feedbacks are important for low frequency SST variability in the North Atlantic in this model.

Received 21 January 2004; accepted 2 April 2004; published 12 May 2004.

Index Terms: 1620 Global Change: Climate dynamics (3309); 3339 Meteorology and Atmospheric Dynamics: Ocean/atmosphere interactions (0312, 4504); 3337 Meteorology and Atmospheric Dynamics: Numerical modeling and data assimilation; 4215 Oceanography: General: Climate and interannual variability (3309); 4255 Oceanography: General: Numerical modeling.

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Citation: Wu, Z., E. K. Schneider, and B. P. Kirtman (2004), Causes of low frequency North Atlantic SST variability in a coupled GCM, Geophys. Res. Lett., 31, L09210, doi:10.1029/2004GL019548.