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Atlantic Ocean

Shifting pressure patterns in the North Atlantic

Effets positifs et négatifs du NAO

One of the most remarkable recurring atmospheric phenomena over the Atlantic makes its presence felt in winter. Called the North Atlantic Oscillation (NAO), it is driven by pressure differences between a high-pressure system over the Azores and a low-pressure system over Iceland, with which the ocean interacts.

From North America to Siberia, regions bordering the Atlantic are exposed in turn to rain or drought, cold or mild temperatures, and strong winds or dead calm.
We have observed weather variations in this way since the 17th century. But it was only when satellites arrived on the scene that we could begin continuous, long-term monitoring of the oceans and atmosphere to unlock the secrets of the mechanisms that drive our weather. Improving our understanding of these variations over periods of ten years and more is key to reliable climate forecasting. In this respect, the permanent ocean-observing capability afforded by altimetric satellites, in combination with other satellites and in-situ measurements, is a vital aid.

What is the NAO ?
Explanation of the phenomenon : positive and negative phases.
Observations
Since the middle of the 19th century, the North Atlantic Oscillation has been measured from land and, increasingly, at sea. In recent years, satellites have made it possible to monitor this phenomenon continuously and systematically. Example with a sharp variation in 1995 - 1996.

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