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Gudrun Magnusdottir

Chair and Professor, Dept of Earth System Science, University of California-Irvine

Forcing of the wintertime atmospheric circulation by multidecadal fluctuations of the North Atlantic ocean

Room 811 AOSS, April 10, 2017, 3:30 PM

Abstract

The feedback of extratropical sea surface temperature on the atmosphere is weak on interannual time scales. However, recent evidence suggests that the long-term variability of sea surface temperature in the North Atlantic, referred to as Atlantic Multidecadal Variability (AMV), may exert a significant influence on the atmospheric circulation in the Northern Hemisphere. In particular, analyses using observations/reanalyses, as well as numerical experiments using different configurations of the Community Atmospheric Model version 5 (CAM5), suggest that the AMV exerts an influence on decadal trends of the wintertime North Atlantic Oscillation (NAO). Coupled ocean-atmosphere preindustrial control simulations of the Climate Model Intercomparison Project (CMIP5) are examined in order to assess whether state-of- the-art global climate models capture such a relationship. Multiyear persistence of the wintertime NAO is a driver of the AMV in these simulations, but no consistent feedback of the AMV onto the atmosphere is identified. Comparisons of model output to observations must be done with caution due to the uncertainties in long-term observations. However, the lack of internally-generated AMV and associated surface heat flux variability in the models seems to limit their capability to capture the full AMV-NAO relationship.



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