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Recent previous research has established the "sharpest gradient" approach to defining the circumpolar vortex and has identified correlations of the area and circularity of the Northern Hemisphere's circumpolar vortex (NHCPV) to important atmospheric-oceanic teleconnections. However, because geographical shifts in the NHCPV, independent of area or circularity changes, could affect surface environmental conditions, this research addresses the question of the extent to which the NHCPV centroid undergoes such shifts, both intra- and inter-annually. Results show that during the 1979-2017 period, the centroid has moved less on a daily basis in more recent years, perhaps indicative of a stabilization in circulation, with annual and semi-annual periodicities in the daily distance moved. A consistent preference toward the Eastern Hemisphere is evident by the displacement of the centroids toward the Pacific basin throughout the study period. Collectively, these results indicate the mid-tropospheric response to the near-surface warming.

Plain Language Summary Our previous research developed an approach for delineating the leading edge of the boundary of the cold polar air circulation. This research identifies the position of the center of this polar circulation in the Northern Hemisphere, on a daily basis, from 1979 through 2017. We find that this centroid's position has stabilized over time while maintaining a preferred position on the Eastern Hemisphere side of the North Pole. These results are important because they suggest that the middle-to-upper weather layer in the atmosphere may responding slowly to the near-surface warming over the last few decades.

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