Initiation of East Asia monsoon failure at the climate transition from the Medieval Climate Anomaly to the Little Ice Age

- We estimated SST and SSS of the East/Japan Sea over the last 1300 yr.
- East Asia monsoon variability has been reconstructed over the period.
- A strengthened summer monsoon occurred for the MCA at time of negative PDO.
- Asian monsoon failure started at the end of the MCA and extended to the LIA.

We have reconstructed decadally-resolved continuous sea surface temperature and seawater δ18O (hence salinity) records over the last 1300 yr from alkenone and planktonic foraminiferal oxygen isotope ratio analyses of the East Sea/Japan Sea marine sediments to investigate East Asia monsoon variability. Comparisons of the records with other paleoclimate records indicate a possible connection between changes in the mid-latitude East Asia monsoon and Pacific Decadal Oscillation (PDO) over this period. The results show that during the Medieval Climate Anomaly (MCA) when the PDO index was negative, East Asia was characterized by surface warming with a strengthened summer monsoon. Summer monsoon-related precipitation increased and pluvials possibly dominated in the region at that time. Onset of Asia monsoon failure and severe drought occurred at the end of the MCA and extended to the Little Ice Age (LIA) when the PDO became positive.