Transcript North Atlantic Oscillation Joseph Papapietro

North Atlantic Oscillation
Joseph Papapietro
Outline

What is NAO?

Atmospheric changes.

The Atmosphere/Ocean connection.

Biological/Ecological Effects
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.
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.
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.
Weather

Positive NAO:





Negative NAO
Warm in Eastern
North America

Cold in Iceland

Warm/Wet in Northern
Europe
Cool/Dry in
Mediterranean


Cool Eastern North
America [More snow?]
Warmer than usual in
Iceland [Ice melt?]
Cool/dry in Northern
Europe
Warm/Moist in
Mediterranean
Sea Surface Temperature
maps for Positive NAO
(top), and Negative NAO
(bottom).
warm
cool
cool
warm
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.
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://www.whoi.edu/page.do?pid=12455&tid=282&cid=10146 [photos]