2003 Fiscal Year Final Research Report Summary
International Collaboration on the Study of Geodynamics of Subglacial Lake Vostok, Antarctica
| Project/Area Number |
14580556
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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 |
Environmental dynamic analysis
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| Research Institution | National Institute of Polar Research |
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Principal Investigator |
SHIBUYA Kazuo National Institute of Polar Research, Center for Antarctic Environment Monitoring, Professor, 南極圏環境モニタリング研究センター, 教授 (80132710)
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| Co-Investigator(Kenkyū-buntansha) |
DOI Koichiro National Institute of Polar Research, Center for Antarctic Environment Monitoring, Associate Professor, 南極圏環境モニタリング研究センター, 助教授 (80290873)
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| Project Period (FY) |
2002 – 2003
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| Keywords | Lake Vostok / Synthetic Aperture Radar / Lake Tide / GPS vertical motion / Subglacial Lake / ice dynamics / Antarctica |
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| Research Abstract |
In 1969, an Askania Gs-11 gravimeter was operated at Vostok Station (78.466°S, 106.832°E, 3478 m asl) by Schneider (1970). We revisited and analyzed the data with a BAYTAP-G and -L (Tamura et al., 1991) program. For the two global ocean tide models of NAO99b (Matsumoto et al., 1999) and FES99 (Lefevre et al., 2000), we estimated the load tides. For the K1 wave, the obtained residual amplitude was 1.91 ± 0.25μ Gal, while for the M2 wave it was 1.24 ± 0.14,u Gal. The associated uncertainty reduced to one-thirds as compared with the results by Dietrich et al. (2001). It is interesting that K1 wave is about 900 phase-leaded, while M2 wave is about 1800 phase-leaded (delayed). With a conversion coefficient of -0.29μ Gal/mm from gravity variation to vertical displacement, the displacement was in the range of about ±10 mm ; which is found to match the actually observed 2002/2003-season GPS vertical motion in a least square sense. Air pressure differences above the lake cause a differential inverse barometer effect with resulting height changes of up to 40 mm on time scales from days to weeks. The effect could be verified, together with the differential tidal motions, by differential GPS observations in the southern part of the lake during the 2002/2003 summer season. The measured amplitudes and phases of the largest constituents correspond to the respective values of the differential equilibrium tides. Four ERS-1/-2 tandem interferograms of 1996 were used to analyze the spatial pattern of the surface displacement. These measurements reveal a bulge with a wide tidal flexure zone of varying amplitude but a similar geometry. Moreover, it can be concluded that the associated water redistribution within the lake forms an additional component of the overall water circulation in the lake
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[Publications] Poetzsch, A., Wendt, J., Dietrich, R., Shibuya, K., Doi, K., Lukin, V., Yuskevich, Senatorov, A.: "Response of subglacial Lake Vostok, Antarctica, to tidal forcing"Terra Nostra. Vol.4. 263-264 (2003)
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