Multidecadal Mobility of the North Atlantic Oscillation

• Published in: Journal of climate Vol. 26; no. 8; pp. 2453 - 2466
• Main Authors: Moore, G. W. K., Renfrew, I. A., Pickart, R. S.
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 15.04.2013
• Subjects: Anthropogenic climate changes; Anthropogenic factors; Atmospheric forcing; Atmospherics; Azores; Climate; Climate change; Climate system; Climatology. Bioclimatology. Climate change; Cluster analysis; Covariance matrices; Dipoles; Earth, ocean, space; Economics; Empirical analysis; Exact sciences and technology; External geophysics; Global climate; Human influences; International trade; Marine; Meteorology; Meteors; Mobility; North Atlantic Oscillation; Ocean-atmosphere system; Orthogonal functions; Paleoclimatology; Precipitation; Pressure; Pressure distribution; Pressure field; Sea ice; Sea level; Sea level pressure; Variability; Winter; North Africa; Azores; Iceland; Greenland; Fram Strait; Iberian Peninsula; Europe; North Atlantic region; time series analysis; Teleconnection; North Atlantic oscillation; Correlation analysis; Change detection; Pressure distribution; Sea level pressure; Empirical orthogonal function; atmospheric pressure
• ISSN: 0894-8755; 1520-0442
• DOI: 10.1175/jcli-d-12-00023.1

The North Atlantic Oscillation (NAO) is one of the most important modes of variability in the global climate system and is characterized by a meridional dipole in the sea level pressure field, with centers of action near Iceland and the Azores. It has a profound influence on the weather, climate, ecosystems, and economies of Europe, Greenland, eastern North America, and North Africa. It has been proposed that around 1980, there was an eastward secular shift in the NAO’s northern center of action that impacted sea ice export through Fram Strait. Independently, it has also been suggested that the location of its southern center of action is tied to the phase of the NAO. Both of these attributes of the NAO have been linked to anthropogenic climate change. Here the authors use both the one-point correlation map technique as well as empirical orthogonal function (EOF) analysis to show that the meridional dipole that is often seen in the sea level pressure field over the North Atlantic is not purely the result of the NAO (as traditionally defined) but rather arises through an interplay among the NAO and two other leading modes of variability in the North Atlantic region: the East Atlantic (EA) and the Scandinavian (SCA) patterns. This interplay has resulted in multidecadal mobility in the two centers of action of the meridional dipole since the late nineteenth century. In particular, an eastward movement of the dipole has occurred during the 1930s to 1950s as well as more recently. This mobility is not seen in the leading EOF of the sea level pressure field in the region.