Recent Studies of the Sea of Okhotsk

We recently have had a Japan-Russia-United States International Joint Project, 1997-2002. In this project, we have carried out intensive oceanographic observations in the almost entire Sea of Okhotsk for the first time, using a Russian research vessel; we have had four times cruises, changing seasons. This report summarizes several new findings for the Sea of Okhotsk which were obtained by this project, for examples, the major location of the sea ice production and its growth history, the structure and seasonal variability of the East Sakhalin Current and its formation mechanism, and the systems of water circulation and material cycle which make this sea to be the area of high biological productivity. Finally, we have found out the warming and oxygen-decreasing trends of intermediate water in the northwestern North Pacific during the past 50 years, originating from the Sea of Okhotsk. This result suggests that the overturning in the Sea of Okhotsk and the North Pacific will be weakened and the resulting go-down of biological productivity is concerned. KEY WORDS; Sea of Okhotsk, Sea ice, East Sakhalin Current, System of material cycle, Coastal polynya