| Project/Area Number |
16403005
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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 | 海外学術 |
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| Research Field |
Meteorology/Physical oceanography/Hydrology
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| Research Institution | Research Institute for Humanity and Nature (2005)
Hokkaido University (2004) |
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Principal Investigator |
SHIRAIWA Takayuki Research Institute for Humanity and Nature, Research Department, Associate Professor, 研究部, 助教授 (90235739)
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| Co-Investigator(Kenkyū-buntansha) |
NAKATSUKA Takeshi Hokkaido University, Institute of Low Temperature Science, Associate Professor, 低温科学研究所, 助教授 (60242880)
TACHIBANA Yoshihiro Tokai University, Center for Education, Associate Professor, 総合教育センター, 助教授 (10276785)
YAMAGATA Kotaro Joetsu University of Education, Department of Education, Associate Professor, 学校教育学部, 助教授 (80239855)
MATOBA Sumito Hokkaido University, Institute of Low Temperature Science, Assistant Professor, 低温科学研究所, 助手 (30391163)
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| Project Period (FY) |
2004 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥9,700,000 (Direct Cost: ¥9,700,000)
Fiscal Year 2005: ¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2004: ¥6,000,000 (Direct Cost: ¥6,000,000)
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| Keywords | Ice core / North Pacific / Climate change / PDO / Iron hypothesis / Alaska / Mount Wrangell / Mount Ushkovsky / 雪氷コア解析 / 古気候変動 / 風送塵 / 氷河 |
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| Research Abstract |
We analyzed the ice core drilled at Mt.Wrangell in 2004. The analyses were made for the upper 100m of the 217-m long ice core. They are hydrogen isotope ratio (0-50m), major ions (0-50m), dust concentration (0-80m), X-ray density (0-100m) and tritium (0-50m). Trace elements were also measured for the Mt.Logan ice core which we drilled in 2002. Following results are obtained by this research project :
1.Clear seasonal cycles are found for the upper 50m of the ice core in the cases of hydrogen isotope ratio, dust and tritium concentrations. The peaks appeared in summer for delta D and spring for the dust and tritium concentrations.
2.Standard deviation in the X-ray density variations are negatively related with delta D suggesting that the high density variations occur in spring-summer period when snow falls rather intermittently.
3.Concentration in dust becomes higher in spring and lower in the other periods. It is also found that the dust concentration has been increasing since 2000, which coincides with observation of dust falls in Japan.
4.Tritium concentration in the Wrangell ice core shows a beautiful seasonal cycle having the highest peak in spring. This is due to the so-called "Stratosphere-Troposphere Exchange" in air mass and the concentration can be a promising indication of atmospheric disturbances in spring.
5.Sodium flux is positively correlated with Pacific Decadal Oscillations suggesting the atmospheric-oceanic interaction in the North Pacific.
6.Annual Iron fluxes during the period 1980-2000 in the Logan ice core were varying from several μg/square m to 80μg/square m. The source of the iron can be ascribed to Asian dust and the nearby volcanoes.
7.Annual accumulation rates both in the Wrangell ice core and the Logan ice core showed clear negative relationship for the last 100 years, suggesting that the PDO has impacted mountain precipitation significantly.
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