Author's Personal Copy Climate Variability during Warm and Cold Phases of the Atlantic Multidecadal Oscillation (amo) 1871–2008

In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: a b s t r a c t a r t i c l e i n f o Keywords: Ocean–atmosphere system Surface temperature Sea level pressure Atmospheric precipitations Reanalysis An extended reanalysis, a combination of observations and model output, is used to examine the spatial patterns of physical variables associated with the Atlantic Multidecadal Oscillation (AMO) from 1871 to 2008. The results are presented as anomalies during positive and negative phases of the AMO. As in previous studies, during positive (negative) AMO phases the sea surface temperature (SST) is anomalously warm (cold) over most of the North Atlantic, with the exception of the east coast of the United States. The atmospheric patterns, associated with the positive phase of the AMO, include anomalous low pressure over the Atlantic between 20°S and 50°N, cyclonic surface winds around the low, reduced wind speeds over the tropical Atlantic and enhanced precipitation in the eastern tropical Atlantic, with roughly opposite conditions during negative AMO phases. There are, however, substantial differences in the SST and the atmospheric anomalies between periods of the same phase, especially in the extratropics. Correlations between the AMO and air temperature anomalies are positive over much of the globe between 40°S and 50°N, with correlations exceeding 0.6 (~95% significance level) over the Maritime Continent and northern rim of the Pacific Ocean. Most of the sea level pressure (SLP) anomalies beyond the Atlantic are not statistically significant. The Atlantic Ocean exhibits variability over a wide range of temporal and spatial scales but has pronounced variability at decadal and multidecadal timescales. While there is an extensive history of studies on decadal variability in the North Atlantic (e. the term Atlantic Multidecadal Oscillation or AMO was first used in an editorial article by Kerr (2000) to describe slowly varying sea surface temperature (SST) anomalies that extend over most of the North Atlantic. The AMO is associated with the North Atlantic's dominant pattern of SST variability, with anomalies of the same sign over most of the basin but with larger anomalies in a horseshoe shape that includes the tropical Atlantic, the eastern portion of the entire basin, and from south of Greenland extending northwestward into …