Coupled Air Sea Interaction in the South Pacific

In the North Pacific, the variability of the sea surface temperature (SST) is dominated by a pattern called the Pacific Decadal Oscillation. Recent analysis of observations and models suggest that this pattern results from a first order, autoregressive (AR-1) process forced by the Aleutian Low, by El Nino, and in the Kuroshio-Oyashio Extension regions by ocean circulation anomalies.

In this study, we employ a similar methodology to explore the variability of SST in the South Pacific. Lacking a long observational record, output from an extended integration of a coupled climate model is used. Results indicate that the SST reconstruction based on an AR-1 model is similarly successful as in the North Pacific. However, in contrast to north of the equator, more than one pattern of atmospheric sea level pressure are essential to explain SST variations. Ocean dynamics, as described by ocean sea level, are important in the East Austral Current, off New Zealand, and in an arc that extends from the tip of South America in the north-westward direction towards 30S. As a result, the SST anomaly pattern in the South Pacific is not dominated by a single pattern, and there is no direct counterpart to the Pacific Decadal Oscillation in the South Pacific. The possible role of ocean to atmosphere feedbacks, detectable but small in the North Pacific, will be explored for the South Pacific.