Abstract:
In 1989, the Ocean Drilling Program (ODP) leg 127 cruise to the Japan Sea recovered a series of Quaternary hemipelagic sediments characterized by millennial-scale rhythmical alternation of dark and light layers, which are traceable basin-wide. Subsequent studies revealed that these dark and light alternations are well correlated with millennial-scale oxygen isotope variations observed in Greenland ice cores, suggesting that they reflect abrupt climatic changes of hemispheric scale. Furthermore, it was demonstrated that deposition of the dark and light alternations was resulted from changes in nutrient flux through the Tsushima Strait, which reflected summer monsoon precipitation over South China. On the other hand, studies on eolian dust component in the Japan Sea sediments demonstrated that dust provenance changed between the Taklimakan Desert and the Gobi Desert in association with the dark and light alterations, suggesting north-south oscillations of the subtropical westerly jet axis. This finding suggests that the westerly jet mediates a tele-connection between East Asian summer monsoon and North Atlantic climate changes on a millennial time scale. The hemipelagic sediments in the Japan Sea preserve a long and continuous record of variation in the East Asian monsoon and its temporal evolution throughout Neogene. Thus the sediments can provide us a unique opportunity to study the onset timing and evolution process of millennial-scale variability of the East Asian monsoon and explore the ultimate cause and amplification and propagation mechanisms of millennial-scale abrupt climatic changes. IODP drilling in the Japan Sea and northern East China Sea is now scheduled in the summer of 2013, and presents a great opportunity for us.