The study looked at how the Arctic Oscillation (AO) pattern changes over decades. They found that the AO pattern in the Atlantic stayed the same from 1920 to 2010, but in the Pacific, it was strong from 1920 to 1959 and 1986 to 2010, and weak from 1960 to 1985. This affected the link between the AO and winter temperatures in western North America. The researchers also discovered that the AO is mainly influenced by atmospheric patterns in the North Atlantic and North Pacific, with the North Pacific mode and North Atlantic Oscillation playing key roles. The AO's circular shape likely comes from how these two patterns interact.