Characteristics of the East Asian summer monsoon in the South Sea of Korea during the Little Ice Age

The sediment record of a drilled core, SSDP-103, and four AMS 14C datings were used to generate oxygen and carbon isotope data over the last 2000 years of the benthic foraminifer Cibicides lobatulus in the South Sea of Korea. High sedimentation rates facilitated a decadal resolution throughout the study period. Significant periodicities of 316, 249, 144, and 88 years were observed in the δ18O record of the benthic foraminifera. Similar periodicities of 310, 220, 143, and 120 years were identified in the δ13C record. These periodicities were close to those of solar origin, which are related to changes in the oceanic and atmosphere circulation in East Asia. The three-point-smoothed δ18O curve of benthic foraminifera in the study area was closely correlated with the stalagmite δ18O record from Chinese caves for the last 2000 years, except during the dramatic cooling interval of the Little Ice Age (LIA). During the cooling period, the benthic foraminifera δ18O values significantly increased, while stalagmite δ18O values decreased. Such an inverse relationship during the LIA reflects synchronous strengthening of the East Asian summer monsoon (EASM) and weakening of the Indian summer monsoon (ISM). Under the present climatic system, an inverse relationship between these two Asian monsoons has frequently occurred when an El Niño event developed. The results suggest that late-Holocene cold events are associated with El Niño-like climatic patterns.