| Project/Area Number |
16310001
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Environmental dynamic analysis
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| Research Institution | Hokkaido University |
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Principal Investigator |
YOSHIKAWA Hisayuki Hokkaido Univ., Facility of Environmental Earth Science., Professor, 大学院地球環境科学研究院, 教授 (60344496)
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| Co-Investigator(Kenkyū-buntansha) |
NORIKI Shinichiro Hokkaido Univ., Faculty of Environmental Earth Science, Professor, 大学院地球環境科学研究院, 教授 (80109511)
NAKATSUKA Takeshi Hokkaido Univ., Low temperature Institute, Associate Professor, 低温科学研究所, 助教授 (60242880)
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| Project Period (FY) |
2004 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥14,500,000 (Direct Cost: ¥14,500,000)
Fiscal Year 2006: ¥4,500,000 (Direct Cost: ¥4,500,000)
Fiscal Year 2005: ¥4,400,000 (Direct Cost: ¥4,400,000)
Fiscal Year 2004: ¥5,600,000 (Direct Cost: ¥5,600,000)
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| Keywords | Carbonate system / Kuroshio / subtropical gyre / Seasonal variation / Long-term trend / Net community production / Bioloogical activity / Carbon isotopic ratio / 二酸化炭素分圧 / 群集基礎生産 / 親生物元素 / 亜熱帯 |
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| Research Abstract |
In order to examine the oceanic CO_2 uptake and factors controlling it in and around Kuroshio, measurements of partial pressure of CO_2 (pCO_2), dissolved inorganic carbon (DIC), stable carbon isotopic ratio (^<13>C/^<12>C) of DIC were made at least four times a year in the western North Pacific Subtropical Gyre (NPSG) over the period from 2004 to 2006. In the NPSG, seasonal variation in pCO_2 was mainly controlled by the temperature and biological activity. The former was caused by the thermodynamic temperature effect on carbonate system. From winter to summer, the net community production was estimated to be in the range from 10 to 26 mmol m^<-2> day^<-1> based on measurements of concentration and ^<13>C/^<12>C of DIC. Dueto the oceanic uptake of anthropogenic CO_2, the pCO_2 in surface seawater has increased at a rate (1.6 μatm yr^<-1>) which is nearly equal to that of the air. In the western North Pacific (5-35°N, 132-142ー°E) the air-sea CO_2 flux over the 1990s was estimated to be in the range from 16 to 52 Mt-C yr^<-1> with a mean value of 32Mt-C yr^<-1>. During winter season, the CO_2 flux south of the Kuroshio was about 3 mole m^<-2> yr^<-1>, which was relatively large as compared with those of the average of the world ocean. We have also examined the relationship between chemical constituents of sinking particles and biological activity in the surface mixed layer. Further, we have developed a eco-system model including nitrogen isotope, and used it to discuss the nitrogen cycle in the equatorial Pacific and the Sea of Okhotsuk. Details of our results are given in scientific journals.
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