HR: 0800h
AN: OS31A-0555    [Abstracts]
TI: Nutrients Variability in the Subtropical Gyres in the Southern Hemisphere
AU: * AOYAMA, M
EM: maoyama@mri-jma.go.jp
AF: Meteorological Research Institute, 1-1, Nagamine, Tsukuba, 305-0052 Japan
AU: WATANABE, S
EM: swata@jamstec.go.jp
AF: Japan Agency for Marine-Earth Science and Technology, 2-15, Natsushima, Yokosuka, 237-0061 Japan
AU: FUKASAWA, M
EM: fksw@jamstec.go.jp
AF: Japan Agency for Marine-Earth Science and Technology, 2-15, Natsushima, Yokosuka, 237-0061 Japan
AB: Nutrients analyses were accomplished on 16,000 samples together with the reference material of nutrients in seawater (RMNS) during R/V Mirai cruise which revisited WHP P06, A10, I03 and I04 in the Southern Hemisphere in 2003/2004. The target nutrients are nitrate, nitrite, phosphate and silicate, respectively. To establish the traceability of nutrients concentrations and to get higher quality data, we used 500 bottles of RMNS in a same lot and 150 sets of RMNSs involving 6 levels of RMNSs of which nutrients concentrations ranged from lower concentration as surface water to higher concentrations exceed the maximum concentrations of nutrients. The precisions of phosphate, nitrate and silicate measurements were 0.18%, 0.17% and 0.16% in terms of median of those at 493 stations, respectively. The nutrients concentrations could be expressed with uncertainties explicitly as a function of nutrients concentration because of the repeated runs of RMNSs. Preliminary comparisons with previous WOCE cruises in 1990s revealed that systematic decrease of nutrients concentrations occupies a layer 100-1000 m in the wide area in the subtropical gyres, in which lower upwelling rate of nutrients rich water are suggested. Although lower lateral transport of the nutrients should be also considered, lower nutrients flux into nutrient-depleted layers might occurs in the regions anyway. In the deeper layers below approximately 3000 m, nutrients data also suggest significant variations at the western part of the Atlantic Ocean. In this talk, we will focus on the global view of the changes of nutrients in the subtropical gyres in the Southern Hemisphere and discuss them with the analytical uncertainty of nutrient concentrations.
DE: 4825 Geochemistry
DE: 4845 Nutrients and nutrient cycling
DE: 4215 Climate and interannual variability (3309)
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting