THE LAST GLACIATION MAXIMUM IN THE SEA OF JAPAN/EAST SEA

Hemipelagic sediments in the Sea of Japan (East Sea) during the last glaciation maximum (LGM) were characterized by centimeter-to decimeter-scale alternations of organic-poor light-gray layers, organic-rich dark-gray layers and homogenous layers. In association with the sedimentary characteristics, the alkenone sea surface temperatures (U^k'37-SSTs) of the central and southern Japan Sea were estimated and the results enabled us to understand the paleoceanographic evolutions in the study area during the LGM and its linkage with the East Asian monsoon (EAM). During 24.2~17.8 cal kaBP,deposition of the laminated layers had good relationship with the strengthening summer EAM,indicating that the EAM precipitation was the main cause for the oxygen-level variation of bottom water in the Japan Sea. The low U^k'37-SSTs in the northern Okinawa Trough during 24.2~17.8 cal kaBP further implied that the strong influx of East China Sea Coastal Water (ECSCW), which was regarded as lower-salinity and nutrient-enriched watermass and derived from the precipitation of summer EAM, had influence on the northern part of the East China Sea. Under the influence of weakened summer EAM or intensified winter EAM, the ventilation of deep water was reinforced and the suboxic or oxic bottom water dominated in the basins of Japan Sea during 30~24.2 and 17.8~15cal kaBP.Why there was the anomaly of high U^k'37-SSTs in the Japan Sea during 23~17.5 cal kaBP was not fully understood so far. It was generally accepted that the ventilation of deep water was blocked during this period by the density stratification of the water column as a result of excessive EAM precipitation, the surface salinity was low and the bottom was filled with static, anoxic water.