The North Atlantic Oscillation (NAO) is a climatic phenomenon in the North Atlantic Ocean that impacts weather and climate patterns in the Northern Hemisphere. It is characterized by fluctuations in the pressure difference between the Azores High and the Icelandic Low.
The concept of the NAO was first introduced by Sir Gilbert Walker in the early 20th century while he was investigating global climate patterns. However, the term "North Atlantic Oscillation" was not coined until later by Edward Lorenz in 1950, who described it as a mode of variability of atmospheric circulation.
The NAO index is calculated based on the difference in the atmospheric pressure at sea level between the Azores High and the Icelandic Low. Here are some key aspects:
The NAO has significant effects on:
Recent studies have shown that the NAO has exhibited trends towards more positive phases, particularly since the mid-20th century. This shift might be linked to anthropogenic climate change, although natural variability also plays a significant role.
Research into the NAO continues, with climate models attempting to predict its future behavior. There is ongoing debate about how global warming will affect the NAO, with some models suggesting a possible increase in the frequency of extreme positive or negative NAO events.