Multidecadal Fluctuations of the North Atlantic Ocean and Feedback on the Winter Climate in CMIP5 Control Simulations

Past studies have shown that 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 winter in the Northern Hemisphere.  Statistical analyses using observations/reanalyses as well as numerical experiments of different configurations of an atmospheric global climate model (CAM5), suggest that the AMV exerts an influence on decadal trends of the wintertime North Atlantic Oscillation (NAO). Coupled ocean-atmosphere simulations of the Climate Model Intercomparison Project (CMIP5) are examined in order to assess whether the 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.  Even though comparisons between model results and observations are problematic due to large uncertainties in long-term observations, a lack of internally-generated AMV and associated surface heat flux variability in the models seems to limit their ability to capture the full AMV-NAO relationship.