Principal Components Analysis (PCA) is performed on seasonal anomalies of the 500 hPa geopotential height fields to isolate the mechanisms causing the decadal change. In SON, PCA reveals that the 1980s teleconnection is weak due to the interference between the Pacific South American pattern (PSA) associated with ENSO and the Antarctic Oscillation (AAO) pattern, especially during the 1988 La Niņa. Regression analysis details that in the 1990s SON the AAO is strongly coupled with the central equatorial Pacific SST anomalies; the AAO is in-phase with the ENSO forcing during this decade producing a strong teleconnection. The in-phase relationship between the tropical and high latitude forcing also exists in DJF during the 1980s and 1990s. Thus, the significantly positive correlation between ENSO and the AAO only during times of strong teleconnection suggest that both the tropics and the high latitudes need to work together in order for ENSO to strongly influence Antarctic climate.
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