2012 Fiscal Year Final Research Report
Changes in surface environments and Earth's interior and Earth's rotational variations
| Project/Area Number |
22540440
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Solid earth and planetary physics
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| Research Institution | Kyushu University |
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Principal Investigator |
NAKADA Masao 九州大学, 大学院・理学研究院, 教授 (50207817)
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| Project Period (FY) |
2010 – 2012
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| Keywords | 地球回転変動 / マントル対流 / コア対流 / マントルレオロジー / 氷床変動 / チャンドラー章動 / D"層 |
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| Research Abstract |
Rapid geomagnetic fluctuations with periods less than a few years, so called geomagnetic jerks, seem to be coincident with changes in Earth’s length of day (LOD) and phase of the Chandler wobble. We indicated that rapid accelerations in the CMB flow can produce torques at the CMB generating observed LOD derivative with ~0.1 ms yr-1, but do not produce much for the polar motion. On the other hand, viscosity of the D” layer of the Earth’s mantle, the lowermost layer in the Earth’s mantle, controls a number of geodynamic processes such as the Earth’s rotational variations due to mantle convection and glacial isostatic adjustment. We showed that the decay of Chandler wobble and semi-diurnal to 18.6 years tidal deformation combined with the constraints from the postglacial isostatic adjustment observations suggest that the effective viscosity in the bottom ~300 km layer is 1019-1020Pa s, and also the effective viscosity of the bottom part of the D” layer (~100 km thickness) is less than 1018Pa s. By considering these results and recent melting events of mountain glaciers and polar ice sheets, we are now studying the Earth’s rotational variations caused by the temporal changes in mantle convection.
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