Abstract The Arctic Oscillation (AO) is one of the key atmospheric circulation modes in the mid‐to‐high latitudes of the Northern Hemisphere. The spatial structure of the spring AO exhibits pronounced interdecadal variation, primarily characterized by a shift of the midlatitude circulation center from the North Pacific Center (NPC) to the North Atlantic Center (NAC). Using reanalysis data sets, this study investigates the causes of the interdecadal change in the AO spatial structure, focusing on the variation in the SAV and its regionally confined downward influence, the NAC‐related teleconnection wave trains, and midlatitude local air‐sea interactions. Results show that since the 1990s, the stratospheric Arctic vortex (SAV) intensifies notably and primarily influences the circulation over the North Atlantic through downward propagation of planetary waves, thereby strengthening the NAC. Similar downward signals are absent over the North Pacific, indicating a regional asymmetry influence of the stratospheric anomalies on the two centers. The enhanced NAC can trigger a Rossby wave train that propagates eastward along the westerly jet across the Eurasian continent and extends into the midlatitude North Pacific, inducing negative geopotential height anomaly over the midlatitude North Pacific, and thus weakening the NPC. Meanwhile, sea surface temperature anomalies in the midlatitude North Pacific and North Atlantic modulate low‐level atmospheric baroclinicity and transient eddy activities, particularly through transient eddy vorticity forcing, further contributing to the maintenance of the interdecadal evolution of both the NPC and NAC. This study advances our understanding of the driving mechanisms of interdecadal changes in the spatial structure of the spring AO.
Zheng et al. (Fri,) studied this question.