Sasai¹, Yoshikazu, Akio Ishida^{1, 2}, Yasuhiro Yamanaka^{1, 3}, Maki N. Aita¹ and Michio J. Kishi^{1, 4}

¹Frontier Research System for Global Change, 3173-25, Showa-machi, Kanazawa-ku, Yokohama, 236-0001, Japan, Tel: +81-45-778-5575, Fax: +81-45-778-5497, E-mail: ysasai@jamstec.go.jp, ²Japan Marine Science and Technology Center, 2-15, Natsushima-cho, Yokosuka, 237-0061, Japan, ³Graduate School of Environmental Earth Science, Hokkaido University, N10W5, Kita-ku, Sapporo, 060-0810, Japan and ⁴Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1, Minato-cho, Hakodate, 041-8611, Japan

Marine ecosystem and chemical tracer studies using two OGCMs

Our group has used two ocean general circulation models (OGCMs) to investigate the biogeochemical cycle. One is coupled with three-dimensional ecosystem model (NEMURO) and another is used for chemical tracer study. The ecosystem model coupled with OGCM is used to investigate the effects of seasonal vertical migration of large zooplankton (copepods) on the ecosystem dynamics. The comparison of two cases with and without the seasonal vertical migration of copepods shows that in the northwestern Pacific and Southern Ocean, the primary production is higher in the case with vertical migration. In these regions, large phytoplankton (diatoms) dominates, and the presence of large zooplankton throughout the year reduces the primary production by large phytoplankton (diatoms). This effect is greatest for diatom bloom. The uptake and distribution of CFC-11 simulated in a high-resolution OGCM has been investigated as a tracer study. The model reproduces meso-scale phenomena, especially eddy processes, coastal upwelling and western boundary currents. The seasonal variability of CFC-11 uptake in the coastal upwelling and marginal seas along the Eurasian Continent depends on the seasonal monsoon and upwelling. The rate of total CFC-11 uptake in these regions is about 7% of the total CFC-11 uptake for the global ocean, because the CFC-11 uptake per unit area is about six times that in the open ocean. This result suggests that uptake in the coastal ocean and marginal seas is important globally for both CFC-11 and anthropogenic CO₂.