Arctic Oscillation

Authored by: Jinping Zhao

Encyclopedia of Natural Resources

Print publication date:  July  2014
Online publication date:  June  2014

Print ISBN: 9781439852583
eBook ISBN: 9781351043847
Adobe ISBN:


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The Arctic Oscillation (AO) is a seesaw pattern in which sea level pressure (SLP) at the polar and middle latitudes in the Northern Hemisphere fluctuates between positive and negative phases. This pattern is obtained by the first mode of the Empirical Orthogonal Function (EOF) of the SLP north of 20°N. The standardized time coefficient of EOF first mode is defined as the Arctic Oscillation Index (AOI), which indicates the polarity of the AO and reflects the atmospheric circulation variation of the lower atmosphere. AO can be easily confused with the North Atlantic Oscillation (NAO), as both indices correlate very well. Some scientists believe that AO and NAO are the same process described in different ways. A coupled signal of AO and a strong fluctuation at the 50 hPa level was identified, which indicates that AO is the surface signature of the Northern Hemisphere Annular Mode. AO not only influences the climate, sea ice, and ocean change in the Arctic but also produces global impacts on surface air pressure and temperature, precipitation, and the frequency and track of storms. The spatial variation of AO was revealed to reflect the variation of spatial area AO dominated. The spatial variation index of AO indicates the three stages of long-term variation of the AO.

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