Dynamics and Mechanisms of Decadal Variability of the Pacific-South America Mode over the 20th Century

In this paper, decadal variability of the Pacific-South America (PSA) Mode is examined from year 1871 to 2008 based on the newly developed ocean and atmosphere reanalysis products. The PSA mode, mirroring the Pacific-North America (PNA) Mode in the Northern Hemisphere, emerges as the second EOF mode of 500mb geopotential height anomalies. The mode displays substantial interannual-decadal variability with distinct timescales between 3-8year and 10-18year, respectively.

 The decadal variability of the PSA mode is found to be associated with the coupled ocean-atmosphere interaction over the subtropical South and tropical Pacific. The subduction of the subtropical temperature anomalies in the South Pacific in conjunction with the tropical-subtropical atmospheric teleconnection plays important role in the decadal variability of the PSA mode.