1. North Atlantic Oscillation Joseph Papapietro

2. Outline What is NAO? Atmospheric changes. The Atmosphere/Ocean connection. Biological/Ecological Effects

3. North Atlantic Oscillation A decade-scale processes that appears to play a major role in regional and global climate dynamics, resulting in weather changes in North America and Europe. The oscillation ranges are due to variability in the permanent pressure system in the sub tropics and in the northern region of the Atlantic.

4. A positive NAO index occurs when there is a large pressure gradient between the Sub-tropic permanent high pressure system and North Atlantic Low pressure system. This results in relatively strong westerlies that run across the Atlantic, carrying warm air from North America to Northern Europe.

5. A negative NAO index occurs when there is a small pressure difference between the Sub-tropic permanent high pressure system and North Atlantic Low pressure system. This results in relatively weak westerlies that drop from Iceland and drag cold air to Northern Europe.

6. Weather Positive NAO: Warm in Eastern North America Cold in Iceland Warm/Wet in Northern Europe Cool/Dry in Mediterranean Negative NAO Cool Eastern North America [More snow?] Warmer than usual in Iceland [Ice melt?] Cool/dry in Northern Europe Warm/Moist in Mediterranean

7. cool warm cool warm Sea Surface Temperature maps for Positive NAO (top), and Negative NAO (bottom).

8. Some Biological Effects relatively Positive NAO for ~40 years The Labrador Sea snow crab have flourished in cooler sea temperatures. Cod larvae low tolerance to warm waters of NE Atlantic. NE N. America - positive NAO brings rain and increased warmth – fresher/nutrient deficient water blocks upwelling of deep salty/nutritious water. Less productivity.

9. Thank You! References: - Pearson, Aria; New Scientist; 1/3/2009, Vol. 200 Issue 2688, p32-35, 4p - http://en.wikipedia.org/wiki/North_Atlantic_oscillation [photos]http://en.wikipedia.org/wiki/North_Atlantic_oscillation - http://www.whoi.edu/page.do?pid=12455&tid=282&cid=10146 [photos]http://www.whoi.edu/page.do?pid=12455&tid=282&cid=10146