ENSO-like interdecadal variability in the Pacific Ocean as simulated in a coupled general circulation model

Citation
S. Yukimoto et al., ENSO-like interdecadal variability in the Pacific Ocean as simulated in a coupled general circulation model, J GEO RES-O, 105(C6), 2000, pp. 13945-13963
Citations number
31
Categorie Soggetti
Earth Sciences
Journal title
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
ISSN journal
21699275 → ACNP
Volume
105
Issue
C6
Year of publication
2000
Pages
13945 - 13963
Database
ISI
SICI code
0148-0227(20000615)105:C6<13945:EIVITP>2.0.ZU;2-Z
Abstract
Spatial and temporal structures of interdecadal variability in the Pacific Ocean are investigated using results from an atmosphere-ocean coupled gener al circulation model (AOGCM). The model shows a basin-wide spatial pattern of the principal sea surface temperature (SST) variability similar to the o bserved one. Both interdecadal and interannual temporal structures of the S ST variability agree well between the observation and the AOGCM. On the oth er hand, a slab ocean model coupled to the same atmospheric model as the AO GCM fails to simulate the observed temporal structure. Therefore the timesc ale of the coupled variability is associated with dynamical processes in th e ocean. A distinct interdecadal mode of the coupled atmosphere-upper ocean temperature variability is found in the AOGCM, with a spatiotemporal struc ture coherent with the SST variability. The mode accompanies an El Nino-Sou thern Oscillation (ENSO)-like spatial pattern of SST and the surface wind a nd behaves like a delayed oscillator in ENSO. A wedge-shaped anomaly patter n of the upper thermocline temperature is formed in the eastern Pacific, an d its northern subtropical signal propagates westward, enhanced by a subtro pical wind forcing at the central basin. Arrival of the subtropical signal at the western Pacific around 20 degrees N switches the anomaly of subsurfa ce temperature in the equatorial region through anomalous oceanic heat tran sport along the western boundary. The travel time of the trans-Pacific sign al in the subtropics appears to be responsible for the timescale of this mo de. The AOGCM successfully simulated the second mode of SST with a major va riation in the midlatitude North Pacific as in the observed SST. In the upp er ocean heat content we found another distinct mode, which is characterize d by a midlatitude-subtropics dipole pattern migrating around the North Pac ific subtropical gyre. However, the associated SST variation of this mode s hows a poor correspondence in the dominant interdecadal modes for the obser ved SST.