North Atlantic Oscillation
Seeing the big picture in the Gulf of Maine

High NAO Index	Low NAO Index
Images: Martin Visbeck, LDEO

4. “El Niño of the Atlantic” alters ocean currents

• The North Atlantic Oscillation (NAO) is similar to El Niño, its more famous "cousin" in the Pacific Ocean.
• The NAO is a natural fluctuation in atmospheric pressure difference between the Icelandic Low and Azores High cells. It is measured by the NAO index.
• Weather in North America and Europe and ocean conditions change dramatically with the NAO.
• High or low NAO phases may persist for several years, and decades may be predominantly one phase or the other.
• The NAO influences the routes of ocean currents and the distribution of water masses including Labrador (cold) Slope Water and Warm Slope Water, which can enter the Gulf of Maine through the Northeast Channel.

NAO Index 1864-2002

Image: Jim Hurrel, NCAR/Climate and Global

< Previous  Next >

1.Seeing the big picture: Introduction
2.Offshore buoys are sentinels of change
3.GoMOOS monitors currents entering the Gulf Of Maine
4."El Niño of the Atlantic" affects the incoming currents
5.Warm or cold currents can penetrate the Northeast Channel
6.Case study: Cold water invades the Gulf of Maine
7.Ripple effects reach bays and estuaries
Acknowledgements