2005 Volume 111 Issue 11 Pages 633-642
The East Asian winter monsoon is characterized by cold and dry air blown out from the Siberian high to the surrounding lows. Cold and dry northwesterly is the most common feature of the winter monsoon around the Japanese islands. This cold wind refrigerates the surface water along the Far East coast of Russia in the Japan Sea. Modern oceanographic observations indicate that sea-ice formation along the coast during the extremely cold winter is an important process for the deep-water formation. Thus, combination of sea-ice and deep-water formation in the Japan Sea is the signal of stronger winter monsoon. Occurrence of the ice-rafted debris (IRD), which is a proxy of sea-ice extend, and of an radiolarian species, Cycladophora davisiana, which is a proxy of cold and oxygenated deep water, might be the two standards of the strength of winter monsoon. We examined the records of two proxies during the last 160 ky in the cores from the Japan Sea. Both records showed the fluctuation with millennial time-scale during oxygen isotope stage 3-5 and they suggested the East Asian winter monsoon fluctuation in the same time-scale. The intervals of frequent occurrence of the IRD and Cycladophora davisiana might suggest the strong periods of the East Asian winter monsoon. The fluctuation of the East Asian summer monsoon during stage 3-5 was recorded as sediment lithology (dark layer), the Japan Sea sediments are very unique marine sediments to obtain both summer and winter monsoon records in a core.
