Language:  GlossaryImagesHelp
 
Home: ABOUT: Ocean-atmosphere interface: Major Oscillations: North Atlantic Oscillation
Advanced Search | an expanded view of Topics and Knowledge in the Atlas
 Login for Members

 Username
 
 Password
 

Forgotten your Password?

Not a Member? Join Now

 
Navigate the Atlas:
 4 SUB-TOPICS:
 5 RELATED TOPICS:
 Topic Overview
 Editors
 
North Atlantic Oscillation Maintained by IOC  
Text-only     Printer-friendly version             
The North Atlantic Oscillation (NAO) is the name scientists have given to the see-saw-like climate pattern long observed over the North Atlantic Ocean. This pattern, or ‘climate mode’, most notably affects the winter weather in Europe and parts of North America, as well as the fish stocks of the North Atlantic. Technically, the NAO is characterized by an oscillating pressure variability between the normally sub-tropical high pressure area located over the vicinity of the Azores (Portugal) and a sub-polar low pressure area over the vicinity of Iceland. In general terms, the high over the Azores and the low over Iceland are regular climatic features, however during winter they experience an intensification, and it is this intensification that denotes an NAO event. Depending on the direction of the pressure intensification, an NAO event is considered either positive or negative. During the positive phase of the NAO, winters in northern Europe tend to be warmer and wetter, while the Mediterranean countries experience less precipitation; conversely, a negative phase of the NAO is generally associated with a colder winter across northern Europe and a wetter one in the Mediterranean.

Scientists are uncertain of the mechanism that drives the North Atlantic Oscillation, however they do know that it is not a purely atmospheric phenomenon, rather it is a result of ocean-atmospheric interactions. An average of 2 or 3 NAO events occur per winter. However, in the last 30 years, the occurrance of positive NAO events has markedly increased. Whether this increase is a natural part of the climate mode, or a result of anthropogenically induced changes to the chemical make-up of the atmosphere (ozone depletion, dramatically increasing levels of carbon dioxide) is currently one of the major questions researchers are trying to answer.

 
A climate index is a tool scientists develop to map basic facts of climate modes in a manner that reveals the basic pattern of the climate mode. The NAO index is derived from the steepness of the pressure gradient between the high and the low pressure systems mentioned above. North Atlantic Oscillation Index depicting postive and negative NAO events. Graphic and source material courtesy of Martin Visbeck of the Lamont-Doherty Earth Observatory
 
 
 
 
All  (8) Websites   (7) Documents   (1)
 All
 
Websites
Joint project between the National Science Foundation and NOAA. Atlantic Climate Variability Experiment Joint project between the National Science Foundation and NOAA. 
NOAA's National Weather Service reference website Climate Prediction Center - NOA NOAA's National Weather Service reference website 
General info on NOA and its links to other climate modes such as the Arctic Oscillation NOAA Arctic Theme Page General info on NOA and its links to other climate modes such as the Arctic Osc...  
Brief introductory page, with links, from the Lamont-Doherty Earth Observatory. North Atlantic Oscillation webpage Brief introductory page, with links, from the Lamont-Doherty Earth Observatory....  
Comprehensive informatin on the NAO The North Atlantic Oscillation Thematic Website Comprehensive informatin on the NAO 
CLIVAR Atlantic seeks to understand and predict seasonal to decadal climate variability in the Atlantic sector, with an initial focus on the North Atlantic Oscillation (NAO) and variability in the tropical Atlantic climate system. Tropical Atlantic Climate Experiment CLIVAR Atlantic seeks to understand and predict seasonal to decadal climate var...  
Documents
Scientific study looking at the phenomena, their effects and present understanding of their underlying cause. North Atlantic Climate Variability: Phenomena, Impacts and Mechanisms Scientific study looking at the phenomena, their effects and present understand...  
976 Topics - 5729 Related Knowledge - 11458 Members - 47 Editors
freeMem:179,078,856 totMem:500,039,680 reqNum:140534 openSessions:0 generationTime:2014/11/24 05:50:18