A 106 year monthly coral record reveals that the East Asian summer monsoon modulates winter PDO variability

The Pacific Decadal Oscillation (PDO) is a dominant climate mode in the Pacific Ocean and thought to be related to seasonal to decadal changes in sea surface conditions. Colonies of long-living Porites coral, widely used to reconstruct monthly to century-scale tropical sea surface temperature and sea surface salinity records, were discovered near Koshiki Island, Japan (31°N, 129°E). A monthly resolved, 106 year δ¹⁸O record revealed that distinct decadal-scale variability was significantly correlated with the PDO index. Our comparison showed 1 to 3 years lead-lag correlation of summer coral δ¹⁸O with the winter PDO index, suggesting that the East Asian summer monsoon (EASM) may act as the driving force of winter PDO variability over the last 100 years. Cross-spectral analysis between the winter PDO index and summer coral δ¹⁸O suggested that recent and future global warming may lead to a more frequent and/or stronger teleconnection between EASM and PDO.