A Comparison of Decadal Climate Oscillations in the North Atlantic Detected in Observations and a Coupled GCM

Abstract Decadal climate variations in the Atlantic Ocean found in observational fields and a coupled general circulation model (CGCM) are investigated. In particular, physical processes responsible for the phase reversal are compared. Observed and modeled decadal variations have dominant periodicities around 12.3 and 9.9 yr, respectively. Both variations show similar spatial features: sea surface temperature (SST) anomalies in the western subtropical Atlantic sandwiched by those with opposite sign to the north and south, and a dipole of sea level pressure anomalies, which resemble the North Atlantic Oscillation. Their temporal evolutions are, however, different from each other, suggestive of different dynamics of the oscillation. In the observations, SST and surface-layer (0–100 m) temperature anomalies move eastward from the subtropical western Atlantic to the European coast along the Gulf Stream. Northward propagation of SST anomalies are also found along the western boundaries including the Gulf of Me...