2000 Fiscal Year Final Research Report Summary
Climatic change and Asian monsoon variation for the last 300 years recorded in coral skeleton of the South China Sea.
| Project/Area Number |
11691114
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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 | 海外学術 |
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| Research Field |
Stratigraphy/Paleontology
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| Research Institution | HOKKAIDO UNVERSITY |
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Principal Investigator |
OBA Tadamichi Hokkaido Univ.Graduate School of Environmental Earth Science, Prof., 大学院・地球環境科学研究科, 教授 (60013588)
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| Co-Investigator(Kenkyū-buntansha) |
MURAYAMA Masafumi Kochi Univ.Marine core center, Asist.Prof., 海洋コアセンター, 助教授 (50261350)
TOYODA Kazuhiro Hokkaido Univ.Graduate School of Environmental Earth Science, Asso. Prof., 大学院・地球環境科学研究科, 助教授 (10207649)
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| Project Period (FY) |
1999 – 2000
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| Keywords | Coral skeleton / Hainan Island / Oxygen isotope / Carbon isotope / Asian monsoon / Mg / Ca / Sr / Ca |
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| Research Abstract |
We collected one coral drilling core of 2.2 m length in Octorber 1999 from the east coast of Hainan Island, China. The following conclusions were obtained by comparing the in situ temperature-salinity record and the high-resolution oxygen carbon isotopic record (ca 200 samples) of a Hainan Island coral (Porites lutea) for the same one-year period (1999-2000).
1. The oxygen isotopic ratios of the coral are clearly affected by both SST and the oxygen isotopic composition of the seawater.
2. Minimum oxygen isotopic ratios occurred in December when surface temperatures were the coldest and the maximum peak occurred in September when surface salinities at the coral site in the South China Sea were the lowest.
3. Using the correlation between the measured oxygen isotopic curve and the estimated curve from the temperature and salinity changes in seawater the following temperature equation for Porites lutea is derived. T=-5.617x(δc-δw)+0.693
4. The growth rate of the coral was slow (0.24 mm/day) in summer from June to September and fast (0.44 mm/day) in winter from December to March.
5. The carbon isotopic ratios of the coral decrease from April and coincide with the start of the rainy season at Hainan Island. This suggests that solar radiation may be the most important factor determining the carbon isotopic ratios in the corals.
6. The maximum peak in carbon isotopic ratios occurred between January and March when SST increased rapidly and the minimum peak occurred in September-October when the annual cycle of turbidity is at a maximum due to the increased outflow
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