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衛星干渉合成開口レーダ法の南極氷床域への適用
https://ir.soken.ac.jp/records/808
https://ir.soken.ac.jp/records/8085c984c62-c7d2-43c4-834c-bdbf1db8cb06
| 名前 / ファイル | ライセンス | アクション |
|---|---|---|
要旨・審査要旨 / Abstract, Screening Result (295.3 kB)
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| Item type | 学位論文 / Thesis or Dissertation(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2010-02-22 | |||||
| タイトル | ||||||
| タイトル | 衛星干渉合成開口レーダ法の南極氷床域への適用 | |||||
| 言語 | ||||||
| 言語 | jpn | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_46ec | |||||
| 資源タイプ | thesis | |||||
| 著者名 |
小澤, 拓
× 小澤, 拓 |
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| フリガナ |
オザワ, タク
× オザワ, タク |
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| 著者 |
OZAWA, Taku
× OZAWA, Taku |
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| 学位授与機関 | ||||||
| 学位授与機関名 | 総合研究大学院大学 | |||||
| 学位名 | ||||||
| 学位名 | 博士（理学） | |||||
| 学位記番号 | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | 総研大甲第462号 | |||||
| 研究科 | ||||||
| 値 | 数物科学研究科 | |||||
| 専攻 | ||||||
| 値 | 16 極域科学専攻 | |||||
| 学位授与年月日 | ||||||
| 学位授与年月日 | 2000-03-24 | |||||
| 学位授与年度 | ||||||
| 値 | 1999 | |||||
| 要旨 | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | The synthetic aperture radar (SAR) is an active remote sensing sensor which can create high resolution backscatter intensity images, and has been use for mapping of coastline and ice streams in the Antarctic ice sheet region for all seasons. Recently, SAR interferometry has been applied to generate a digital elevation model (DEM) and to detect the surface displacements associated with the earthquakes. However, application of the SAR interferometry technique to the ice sheet region in the Antarctic region has not been made enough, and has several problems to be solved.<br /> We used the SAR data received by the Japanese Earth Resources Satellite 1 (JERS-1) from the onboard L-band SAR sensor (23.5 cm wavelength) and those by the European Remote Sensing Satellite 1 (ERS-1) from the onboard C-band SAR sensor (5.7 cm wavelength), to study the ice sheet dynamics in the two regions of the East Antarctic ice sheet.<br /> The first region was the Casey Bay area, and two SAR data sets obtained on 7 December and 10 December of 1991 by ERS-1 were analyzed. The interferometric processing of the two SAR scenes produced clear interferogram on the Zubchatyy Ice Shelf, which can be related to deformations by ocean tide. Although topographic fringes cannot be removed from the overall fringes, they can be considered as within 0.25 cycle (1.4 cm), since the surface undulation of the Zubchatyy Ice Shelf is within 0～40 m height range. When we suppose that the obtained displacement fringes consist only of the vertical component, the vertical change of the Zubchatyy Ice Shelf during 3 days interval is estimated as 41.5 cm at maximum; this change is consistent with the ocean tide change of 35.2 cm predicted from the ORI96 model by Matsumoto et al. (J. Geophys. Res., 100, 25319-25330, 1996). At the transition zone between the ice sheet area and the ice shelf area, the grounding lines can clearly be identified by 1～3 km wide bands of dense displacement fringes in the interferogram. When appropriate values are adopted at the physical properties of ice, and when thickness of ice shelf is assumed as 300 m in the deformation equation by Holdsworth (Ann. Geophys., 33, 133-146, 1977), the width of the transition zone results in around 70 m for the transient-creep model and around 400 m for the elastic deformation model, respectively. These values are smaller by a factor of 5～30 than the actually obtained values of about 2 km at the Zubchatyy Ice Shelf in this study and at the Petermann Gletscher in Greenland by Rignot (J. Glaciol., 42, 476-485, 1996).<br /> The second region was the Sôya Coast area, and three time-serial SAR data sets were obtained on June 16, July 30 and September 12 of 1996 by JERS-1. The three-pass SAR interferometry method was applied to these SAR data, and we generated DEM and estimated the ice flow field around the Sôya Coast area. For simplicity, we assumed that the ice flow during 88 days (2 repeat periods of JERS-1) was constant. Interferometric fringes associated with ice flow/deformation were removed using the two SAR pairs, and the topographic fringes were extracted (three-pass SAR interferometry method). The resultant topographic fringes were converted to the ellipsoidal height base on GRS-80 terrestrial reference frame. There are 23 suitable ground control points (GCPs) in the area concerned, covering the height range from 0 to 600m. The most appropriate DEM was created in order that the model heights fitted the GCP heights in a least squares sense. The obtained DEM grids with a spatial resolution of 50m by 50m have a root-mean-square (rms) error of 15.3m as compared with the GCP heights. As for the GTOPO30 model grids with a 30 arc-second resolution in the same area, similar comparison of the model heights with the GCP heights resulted in an rms error of 131.7m, which is worse than the SAR derived DEM by one order of magnitude. It is also noted that 12 GCPs on the islands and coastal outcropped areas are incorrectly located outside of the land area when mapped in the GTOPO30 contours. Thus, SAR interferometry derived DEM has been proved most accurate in this study area.<br /> The displacement fringes were extracted so that the synthetic topographic fringes were subtracted from the first interferogram. Although the obtained ice flow from SAR interferometry was limited only to the line-of-sight direction, the three dimensional ice flow vectors could be estimated by assuming the ice flow direction. We estimated the ice flow vector field on the assumption that the ice flow direction was consistent with the maximum gradient direction of the ice surface. Moreover, we calculated the maximum shear strain and the dilatation from the estimated ice flow vector field. The larger maximum shear strain values around the marginal areas of the ice stream indicate stronger deformation by stress at the transition zone from the slow ice flow area to the fast ice stream area. There is a good correlation between the negative dilatation area and the relatively positive magnetic anomaly area. Since relatively positive magnetic anomalies indicate relative highs of the subglacial bedrock relief, negative dilatation may mean compression of the ice sheet in the upstream side of the subglacial bedrock highs.<br /> Although more refined analysis should be required with the combined interferograms taken by different wavelength and/or those taken from different look angle, SAR interferometry was shown to be a powerful tool for the studies of ocean tide, ice sheet dynamics and ice sheet mapping in the Antarctic marginal ice zone. | |||||
| 所蔵 | ||||||
| 値 | 有 | |||||
