North Atlantic oscillation
![](/Images/godic/202501/30/Nao_indices_comparison5802.jpg")
![Winter index of the NAO based on the difference of normalized sea level pressure (SLP) between Lisbon, Portugal and Stykkisholmur/Reykjavík, Iceland since 1864, with a loess smoothing (black)](/Images/godic/202501/30/Winter-NAO-Index.svg5802.png")
The North Atlantic Oscillation (NAO) is a weather phenomenon in the North Atlantic Ocean of fluctuations in the difference of atmospheric pressure at sea level between the Icelandic low and the Azores high. Through fluctuations in the strength of the Icelandic low and the Azores high, it controls the strength and direction of westerly winds and storm tracks across the North Atlantic. It is part of the Arctic oscillation, and varies over time with no particular periodicity.