並列タイトル等南パタゴニア氷原 Pío XI 氷河における気候以外の要素に影響を受けた末端位置・表面標高・流動変化
一般注記This thesis studies changes of calving glacier under a infuluence of non-climatic forcings. To investigate the long-/short term changes of Glaciar Pío XI, I measured ice-front position, surface elevation, and ice velocity during a period of 2000–2021 by utilizing satellite remote sensing techniques. The focus of the study was relationships between galcier variation and sediment deposition infront of the glacier terminus and lake level drop event, which both were identified by this study. Most of the ice-fronts showed advancing trends over the study period. The greatest advance (1,400 m from 2000 to 2018) was observed at the southern terminus. The northern terminus and some of the subsidiary ice-fronts advanced by several hundred meters during the same period. Glacier-surface elevation increased at a rate increasing from 1.14 ± 0.03 m a−1 in 2000–2007 to 2.69 ± 0.04 m a−1 in 2007–2017/18. If we assume this elevation change is totally due to ice thickness change, the mass gain is equivalent to 4% of the mass loss in the SPI from 2000 to 2015/16. Our data demonstrated that Glaciar Pío XI is one of the most rapidly thickening glaciers in the world. Satellite images indicated sediment deposition and formation of a mound in front of the southern terminus, the mound covered ~80% of the width of the ice-front in October 2018. Satellite data showed rapid drainage of the lake from April to July 2020, resulting in decrease in the lake area by 14.5 ± 0.02 km2 and drop in the water level by 18.3 ± 1.2 m. Water volume released from the lake was 3.7 ± 0.2 km3 (3.7 ± 0.2 Gt), which is one of the greatest among ever reported glacial lake outburst events. Satellite images and DEMs indicated that the outburst was triggered by the collapse of a bump near the lake outlet and subsequent change in the flow path of the outlet stream. The event affected the gravity field, which was observable by the GRACE mascon solution. After the drainage event, characteristics changes are observed at the northern terminus of Glaciar Pío XI. First, the terminus showed rapid retreat (−300 m) and thinning after the drainage event. Glacier velocity of the northern terminus dropped by 60% after the drainage event within 2weeks since the onset, subsequent slow-down was resulted in 92% reduction in the velocity than the velocity before the drainage event. Further, the seasonal change in velocity of the terminus observed before the event was not confirmed form the timeseries of the velocity. Furthermore, the spatial distribution of glacier indicated changes in the primary flow direction from towards the northern terminus to towards the southern terminus. This study revelaed i) recent changes in ice-front position, surface elevaiton, and ice speed of Glaciar Pío XI, ii) sediment deposition in front of a glacier terminus have strong influece to the variation of the glacier, and iii) change in lake level have a strong influence to changes in ice-front position, surface elevation, and ice velocity. Thus, results of this study present a case study which variation of a calving glacier is strongly affected non-climatic forcing, and emphasize that non-climatic forcings shoud be considered for the future projection of calving glaicer.
(主査) 教授 杉山 慎, 教授 Ralf Greve, 教授 渡辺 力, 助教 箕輪 昌紘, 教授 藤田 耕史 （名古屋大学大学院環境学研究科）
環境科学院（地球圏科学専攻）
コレクション（個別）国立国会図書館デジタルコレクション > デジタル化資料 > 博士論文
受理日（W3CDTF）2023-03-02T11:18:11+09:00
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