The causal role of South China Sea on the Pacific-North American teleconnection pattern

The Pacific-North American (PNA) teleconnection pattern is shown to be remarkably influenced by the South China Sea (SCS), through causal inference with information flow, a real physical notion which has just been rigorously derived from first principles. The information flow rate, which measures the strength of causality from the Pacific sea surface temperature anomaly (SSTA) to the PNA index, shows a distinct causal pattern within the SCS. This pattern is rather robust; it exists with different datasets, and lasts through time. To validate, sensitivity experiments have been designed with purported SCS warming and cooling. By comparing the forced PNA evolutions to the standard case, PNA-like responses have been revealed. Specifically, relatively strong positive (negative) SCS SSTA would trigger a positive (negative) propagating PNA-like response. The responding wave train carries energy toward Pacific and North America, and hence affects the PNA growth. Also located is the wave origin using the Rossby wave source diagnosis. This study suggests that the SCS effect should be taken into account in interpreting and predicting PNA.

Automated summary

The study demonstrates the significant influence of the South China Sea on the Pacific-North American (PNA) teleconnection pattern through causal inference with information flow. It reveals a robust causal pattern within the South China Sea and shows that anomalies in the South China Sea sea surface temperature can trigger PNA-like responses. This suggests that the South China Sea effect should be considered when interpreting and predicting the PNA.