The influence of Pacific-North American teleconnection on the North Pacific SST anomalies in Wintertime under the global warming

The impact of the enhancing Pacific-North American teleconnection (PNA) on the intensity of the first mode of SST anomalies (SSTa) in wintertime North Pacific [known as the Pacific decadal oscillation (PDO)-like SST pattern] under global warming is studied using reanalysis datasets and 12 selected CMIP5 models. The robust observational result of the PNA one month ahead of the PDO shows that the PNA has a great effect on the PDO-like SSTa. The intensities of PNA and PDO are defined with elimination of the ENSO signals to evaluate the direct impact of PNA on the PDO in the North Pacific under global warming. By comparing RCP8.5 and historical scenario of selected multi-models (PNA enhanced models), future projection illustrates that the PDO intensity will intensify 2.2 times its internal variability. Approximately 67% of the increase in PDO variations is contributed by the PNA-induced SSTa in the future warming scenario of multi-models ensemble mean. Models with stronger intensification of PNA variability tends to have larger magnitude of SSTa response in the North Pacific, which has more contributions to the enhancement of PDO intensity change in a warmer climate. This may shed some light on the projection of PDO variability and the relative role of PNA forcing under the global warming.

Automated summary

This study investigates the impact of the enhancing Pacific-North American teleconnection (PNA) on the intensity of the first mode of winter-time North Pacific sea surface temperature anomalies (SSTa) under global warming. The results suggest that the PNA has a significant effect on the intensity of the sea surface temperature anomalies. Future projections indicate that the intensity of the sea surface temperature anomalies will increase 2.2 times under the influence of the enhancing PNA.