On the origins of North Atlantic decadal variability: the role of ocean-atmosphere coupling

In this paper, the origins of North Atlantic decadal variability are explored in a series of coupled ocean-atmosphere surgical simulations. The model control simulation captures the major features of the observed North Atlantic decadal variability. The simulated North Atlantic SST anomalies exhibit two distinctive modes: an interannual to decadal tripole mode, and a decadal to multidecadal monopole mode. The coupled modeling surgery studies suggest the critical role of ocean-atmosphere coupling in sustaining the North Atlantic decadal oscillation. The coupling in the North Atlantic is characterized by a robust NAO-like atmospheric response to the SST tripole anomaly. This response is further examined in the coupled AOGCM experiments where a mixed-layer temperature anomaly is initiated but under different coupling configuration.