Upper Oceanic Temperature Variations during 1950-1998 associated with the Pacific Decadal Oscillation (PDO)

The analysis of upper ocean temperature observations, surface winds from the NCEP/NCAR reanalysis, and an Ocean General Circulation Model (OGCM) forced with air-sea fluxes derived from the reanalysis during 1950-2000 will be presented. Several characteristic features of the Pacific Decadal Oscillation (PDO) are obtained. An approximate north-south symmetry across the equator is found in the sub-surface temperature anomalies, although the amplitude in the South Pacific is somewhat weaker than its North Pacific counterpart. Pronounced temperature anomalies are found in the sub-surface western equatorial Pacific, which are out of phase with the local sea surface temperature (SST) and also temperatures in the eastern equatorial Pacific. In the North and South Pacific Ocean, while the near-surface temperature anomalies show an anticyclonic rotary movement around the subtropical gyre, the sub-surface temperature anomalies show a subduction pathway propagating from the middle latitudes toward the equator. Phase relationships for the PDO signals in various parts of the Pacific Ocean are presented.