Relationship between early summer precipitation in Japan and the El Niño-Southern and Pacific Decadal Oscillations over the past 400 years

The El Niño-Southern Oscillation (ENSO) appears to strongly influence East Asian Summer Monsoon (EASM) rainfall, but the relatively short instrumental rainfall record hinders the development of a longer-term understanding of this teleconnection. To partially overcome this issue, here we reconstruct precipitation from tree-ring oxygen isotopes (δ18O) in central Japan during AD 1612-1935. Our results indicate that tree-ring cellulose δ18O is significantly correlated with May-June (MJ) precipitation, allowing us to investigate the link between the EASM summer rainfall and ENSO over the past 400 years. Time- and frequency-domain comparison of the tree-ring δ18O record and recent ENSO reconstructions reveal a common high-frequency (3-8 year) variability that characterized the mid-17th, late 18th and late 19th centuries. Similar analyses of instrumental MJ precipitation and several ENSO indexes during the 20th century indicate that this high-frequency oscillation reappeared from AD 1980. Comparison of ENSO and Pacific Decadal Oscillation (PDO) indexes indicates that the ENSO-EASM teleconnection is strong when ENSO variance is high, and the PDO phase may modulate the ENSO-EASM relationship over the past 400 years.