Is the observed NAO variability during the instrumental record unusual?

• Published in: Geophysical Research Letters
• Main Authors: Semenov, Vladimir, Latif, Mojib, Jungclaus, J., Park, Wonsun
• Format: Article in Journal/Newspaper
• Language: English
• Published: AGU (American Geophysical Union) 2008
• Subjects: North Atlantic; North Atlantic oscillation
• Online Access: https://oceanrep.geomar.de/id/eprint/8413/; https://oceanrep.geomar.de/id/eprint/8413/1/180_Semenov_2008_IsTheObservedNaoVariability_Artzeit_pubid9856.pdf; https://doi.org/10.1029/2008GL033273

Observed multidecadal variability (30 yr running means, trends, and moving standard deviations) of the North Atlantic Oscillation (NAO) during the instrumental record is compared to that simulated by two different coupled general circulation models in extended-range control experiments. Simulated NAO exhibits strong low frequency fluctuations, even on multi-centennial time scale. Observed multi-decadal NAO variations agree well with the model variability. Trend probability distribution functions, observed and simulated, were not found to be different with statistical significance. Thus, multi-decadal NAO changes similar to those observed during the instrumental record, including the recent increase in 1965–1995, may be internally generated within the coupled atmosphere-ocean system without considering external forcing.