Introduction | El Niño and La Niña (ENSO) | NAO and Artic Oscillation

NAO and Artic Oscillation

El Niño is not the only wild climate event that affects regions of the globe! Other variations in atmospheric pressure also affect weather patterns and climate.

The North Atlantic Oscillation

Depending where you live, you may have noticed that some winters have more snowstorms or cold weather than others. The North Atlantic Oscillation (NAO) affects winters in many places in the Northern Hemisphere. The NAO refers to the changes in pressure systems in the Atlantic, which affects weather in many parts of the Northern Hemisphere between November and April.

When there is a strong high-pressure center in the middle of the North Atlantic Ocean and a strong low-pressure center near Iceland, strong winds blow across the ocean. The winds blow large winter storms into the eastern United States. In Europe, the winter is warmer and wetter and the winter in Greenland and northern Canada is cold and dry.

When the area of high and low pressure is weaker, the winds are also weaker, and fewer, smaller winter storms are whisked across the Atlantic. Winter in the Mediterranean is rainy while northern Europe is cold and dry. Winter along the eastern coast of the United States is colder and Greenland's winter is not as cold.

The Arctic Oscillation

The changes in a low-pressure center over the North Pole are called the Arctic Oscillation. When the low pressure is very strong, winds are also very strong. The speedy winds circle around the Arctic trapping cold air at the North Pole. When the low-pressure center is weaker, the winds are also weaker and do not circle around the Arctic with as much speed. This allows cold air from the North Pole to move south into North America, Europe, and Asia.