Activity Report of the National Committee for
the Physical Sciences of the Oceans
Kimio HANAWA Chair of the National Committee for the Physical Sciences of the Oceans
he former, 19th Term, National Committee for the Physical Sciences of the Oceans, Science Council of Japan ended in September 2005, and the present, 20th Term, committee began its activity in October 2006. The members of the National Committee for the Physical Sciences of the Oceans are listed at the end of this report. In this report, recent progress in physical and chemical oceanography in Japan is briefly reviewed for several research fields. Each member of the committee contributed in the preparation of this document. T
1. Research on the Kuroshio
Since the Kuroshio plays an important role in global climate changes and has impacts on the local Japanese coastal areas, it is the major research target of numerous Japanese oceanographers. Fluctuations of the Kuroshio axis were detected with a spatial resolution of one third degrees of latitude and longitude, and a temporal resolution of 7 days, from late 1992 through 2006, using satellite altimeter data combined with surface drifting buoy data. An interesting result is the evolution of the stationary large meander of the Kuroshio south of Japan which occurred in 2004, suggesting that a small seamount located south of Kii-Peninsula may play an important role in the transition from the non-large meander path to large meander path; its importance has already been pointed out by a numerical experiment study. Interactions between the Kuroshio and mesoscale eddies have also been investigated by data analyses and numerical experiments; especially, small meanders of the Kuroshio southeast of Kyushu have attracted attention because they might be a trigger of the stationary large meander of the Kuroshio. The existence of the Ryukyu Current was suggested early 2000’s; a considerable amount of water associated with the Current may be flowing east of the Ryukyu Islands to join the Kuroshio flowing out of the East China Sea through the Tokara Strait. Various oceanographic observations and numerical studies were carried out to reveal the Current. Also, oceanographic observations were carried out intensively east of Taiwan to better understand the flow field of the Kuroshio; they include observations using long-range ocean Radars as well as conductivity-temperature-depth recorders (CTD’s), acoustic Doppler current profilers (ADCP’s), etc.
2. Hydrographic Research on Three-dimensional Oceanic Structure and Circulation
Full-depth high-quality hydrographic observations were conducted as revisits of the WOCE (World Ocean Circulation Experiment) Hydrographic Programme (WHP) observations; other observations were conducted to clarify deep circulation. The former were carried out by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) with R/V Mirai for WHP P6, A10, and I3/I4 along the latitude circle at 20°S − 30°S during August 2003 − January 2004 and for WHP P10 along approximately 149°20′E in 2005 (URL: http://www.jamstec.go.jp/iorgc/ocorp/data/post-woce.html). The latter were conducted centrally by the Ocean Research Institute, The University of Tokyo with R/V Hakuho Maru in the Northwest, Central, and Northeast Pacific Basins (partly a revisit of WHP P15) in 2003, 2004, and 2005, including velocity measurements using lowered acoustic Doppler current profilers (LADCP) and moored current meters. Studies on deep circulation currents and long-term changes of deep water in the Pacific Ocean progressed by analyses of the hydrographic data obtained in this decade. These data were also used for study on surface and intermediate water masses such as the Subtropical Mode Water.
3. Japan Argo Project
The Japanese community participated in the International Argo project through the "Millennium Project" promoted by the Japanese government (2000-2004). Since 2005, JAMSTEC, Japan Meteorological Agency, and other agencies, including university groups, have continued to deploy Argo floats using independent research funds. In order to effectively manage the Japanese Argo project (Japan Argo), a new promotion committee was established in 2005 (URL: http://www.jamstec.go.jp/