Interdecadal Variability at Northern High Latitudes

Abstract

Examination of the 130-year time series of observed surface air and sea surface temperature anomalies for the northern hemisphere reveals three fundamental timescales of variability: interannual, interdecadal and century. Many of the interannual signals can be associated with strong ENSO warming events originating in the tropical Pacific. The century-scale upward trend, on the other hand, is commonly believed to represent evidence of global warming due to the increase of greenhouse gases caused by the activities of mankind. The interdecadal signal, however, is less well understood; many investigators have suggested that it originates in middle-to-high latitudes and is related to decade-to-century scale ocean current fluctuations in the northern North Atlantic (Bjerknes, 1964; Bryan and Stouffer, 1991; Kushnir, 1994).