Evolution of Interdecadal Variability in Sea Level Pressure, Sea Surface Temperature, and Upper Ocean Temperature over the Pacific Ocean*

Abstract

Abstract Interdecadal variability in sea level pressure (SLP) and sea surface temperature (SST) anomalies in the Pacific Ocean was “quasiperiodic” from 1900–91. The coherent variability of this phenomenon is investigated using gridded observational data from the turn of the century (SST and SLP) and of upper ocean heat content (HS) from the recent two and a half decades. The nominal cycle in atmosphere–ocean variables is roughly two decades long, but growth and decay can happen on a shorter timescale (e.g., half a cycle or so). The authors divide the full cycle into four phases: An onset phase, during which a weak SLP anomaly pattern off Japan takes approximately 2–4 yr to expand eastward, leads to large SLP anomalies in the region of the Aleutian low. A quasi-stationary growth phase, with the midlatitude SLP anomaly pattern in the eastern ocean, intensifies over a 2–4-yr period. The persistent SLP anomalies evolve in concert with large SST (and HS anomalies) of the same polarity located to the south-sout...