| Project/Area Number |
12304028
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Stratigraphy/Paleontology
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| Research Institution | Tohoku University |
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Principal Investigator |
IRYU Yasufumi Institute of Geology and Paleontology, Graduate School of Science, Tohoku Univ. Associate Prof., 大学院・理学研究科, 助教授 (00250671)
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| Co-Investigator(Kenkyū-buntansha) |
MATSUDA Hiroki Department of Earth Sciences, Faculty of Science, Kumamoto Univ. Prof., 理学部, 助教授 (80274687)
MATSUDA Shinya College of Education, University of the Ryukyus Associate Prof., 教育学部, 助教授 (30157317)
OMURA Akio Department of Earth Sciences, Faculty of Science, Kanazawa Univ. Professor, 理学部, 教授 (70019488)
SUGIHARA Kaoru Department of Earth System Science, Faculty of Science, Fukuoka Univ. research Associate, 理学部, 助手 (90320275)
YAMADA Tsutomu Institute of Geology and Paleontology, Graduate School of Science, Tohoku Univ. Research Associate, 総合学術博物館, 助手 (50321972)
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| Project Period (FY) |
2000 – 2002
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| Project Status |
Completed (Fiscal Year 2002)
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| Budget Amount *help |
¥46,740,000 (Direct Cost: ¥41,400,000、Indirect Cost: ¥5,340,000)
Fiscal Year 2002: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000)
Fiscal Year 2001: ¥21,190,000 (Direct Cost: ¥16,300,000、Indirect Cost: ¥4,890,000)
Fiscal Year 2000: ¥23,600,000 (Direct Cost: ¥23,600,000)
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| Keywords | hermatipic coral / carbon isotope / oxygen isotope / skeleton / sea surface temperature / Kikai-jima / paleoceanography / diagenesis / 古海洋 |
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| Research Abstract |
Intensive investigations have been conducted on skeletal records of hermatypic corals from Kikai-jima and Guam. They have led to the following two conclusions.
1. We collected fossil hermatypic corals from the Holocene terraces on Kikai-jima, nor them Ruckus. The corals have net been diagenetically altered. Coral δ^<18>(δ^<18>) indicates that sea surface temperature (SST) were equal to or somewhat cooler than the present (25.4℃) during 6.3-8.1 ka in Kikai-jima and that it was lower than the present by 3℃ and 1℃ during 3.1-6.3 ka and 1.4-3.1 ka, respectivety.
2. We have examined skeletal records in a 213-year coral core (Porites lodata), GD2, from Double Reef, Guam. δ^<18>O_<coral> shows seasonal fluctuations with small amplitudes of 0.23-0.57%_o (VPDB) for the years 1980-2000. A stronger statistical relationship exists between SST and δ^<18>O_<coral> for El Nino years (γ=-0.81) and non-ENSO years (El Nino/Southern Oscillation) (γ=-0.66) than for La Nina years (γ=-0.48). These different statistical relationships are a manifestation of changes in the winter season SST and changes in seawater δ^<18>O (δ^<18>O_<sw>) during El Nino (<27℃) versus la Nina periods (>21℃) at Guam, which reflects the migration of Western Pacific Warm Pool (WPWP). In the winter season of EI Nino periods, Guam Island is surrounded by a relatively low SST and high SSS water mass due to eastward migration of WPWP, which is recorded in GD2 as a relatively Large amplitude of seasonal SST and positive anomalies δ^<18>O_<sw>. In contrast, in the winter season of La Nina periods, SST exceeds 28℃ and SSS becomes greater by increases in evaporation and decreases in precipitation due to the westward migration of WPWP. These changes result in much smaller changes in seasonal SST foe La Nina periods El Nino periods to El Nino periods and in positive δ^<18>O_<sw> anomalies.
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