Changing Relationship between the Pacific Decadal Oscillation and North Pacific Meridional Mode in a Warming Climate

The Pacific Decadal Oscillation (PDO) and the North Pacific Meridional Mode (NPMM) are prominent climate modes in the North Pacific. Recent research has highlighted the influence of NPMM on PDO variability. However, how the relationship between these two modes will evolve from historical to future climates remains uncertain. This study investigates the evolving relationship between the NPMM and PDO under a warming climate. The shift in the NPMM-PDO relationship is attributed to changes in the NPMM and the El Niño-Southern Oscillation (ENSO) transition cycle. Results from the Community Earth System Model Version 2 large ensemble suggest that external forcing has played a key role in triggering these shifts. Additionally, our findings indicate that the influence of NPMM on PDO weakens in future climates due to altered tropical teleconnection patterns and enhanced NPMM intensity, which can further modify the PDO pattern, offering new insights into North Pacific climate variability projections.