Quasi-decadal and inter-decadal climate fluctuations in the Pacific Ocean from a CGCM
Yves M. Tourre, Carole Cibot, Laurent Terray, Warren B. White and Boris Dewitte
Diagnostic analyses in the Pacific, have revealed distinct quasi-decadal (QD) and inter-decadal (ID) climate fluctuations with coherent varying patterns of sea surface temperature (SST) and sea level pressure (SLP) anomalies. From a 200-year CGCM simulation, distinct low-frequency fluctuations are also obtained: QD (i.e., 8–12 years period band) and ID (i.e., 18–25 years period band). Traced modeled QD evolution reveals equatorial SST anomalies resembling ENSO, while tropical recharge/discharge mechanisms seem to be operating. The traced modeled ID evolution reveals high latitudes spatially coherent patterns, with maximum SST anomalies in the vicinity of the subarctic frontal zone (SAFZ) and subtropical gyres through advection. Contrary to QD SST anomalies, the modeled ID SST anomalies peak away from the equator as observed. QD fluctuations may then be viewed as lowfrequency ENSO phenomena, while ID fluctuations may set-up thermal background modulating frequency and intensity of ENSO.