Interaction of the solid Earth and the Antarctic ice sheet

第6回極域科学シンポジウム分野横断セッション：[IG] 全球環境変動を駆動する南大洋・南極氷床11月17日（火）　国立極地研究所 2階 大会議

ヘンイ ソクド ノ チイサナ ヨコズレ カツダンソウ ノ ソンザイ オヨビ コジシン カツドウ ノ カンチ ニ カンスル ケンキュウ

京都大学0048新制・課程博士博士(理学)甲第10584号理博第2726号新制||理||1394(附属図書館)UT51-2004-G431京都大学大学院理学研究科地球惑星科学専攻(主査)教授 岡田 篤正, 教授 竹村 恵二, 助教授 堤 浩之学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDA

Report on geomorphologic and geologic field surveys in central Dronning Maud Land, 2015-2016 (JARE-57)

Geomorphologic and geologic field surveys were conducted in central Dronning Maud Land during the summer of 2015-2016 as part of the 57th Japanese Antarctic Research Expedition (JARE-57). The members of the field expedition included three geomorphologists, a geologist, and a field assistant. This field expedition was fully supported by the Norwegian Polar Institute (NPI) and the South African National Antarctic Program (SANAP), and it was the first JARE expedition to use the Troll and SANAE stations. The NPI provided airborne access from Germany (Norway, on the way back) to the Troll station in central Dronning Maud Land via Cape Town, South Africa. The SANAP provided a helicopter to access nunataks and mountains in this area from the Troll and SANAE stations. This report summarizes the activities of this field expedition including fieldwork, logistics, and weather observations

Perspectives on a Seamless Marine-lake Sediment Coring Study in East Antarctica

The Antarctic Ice Sheet (AIS) is one of the largest potential contributors to future sea-level changes. Recently, an acceleration of AIS volume loss through basal melting and iceberg calving has been reported based on several studies using satellite observations, including radar altimetry, interferometer, and gravity measurements. A recent model that couples ice sheet and climate dynamics and incorporates hydrofracturing mechanism of buttressing ice shelves predicts a higher sea-level rise scenario for the next 500 years. However, the calibration and reproducibility of the sea-level rise projection from these models relies on geological sea-level reconstructions of past warm intervals. This suggests that a highly reliable reconstruction of the past AIS is essential for evaluating its stability and anticipating its contribution to future sea-level rise. In particular, a relative sea-level reconstruction in East Antarctica is the key to solving the problems and refining future projections. The current understanding of sea-level change along the East Antarctic margin is reviewed, including Glacial Isostatic Adjustment (GIA) effects, and a new strategy is proposed to address this topic based on seamless sediment coring from marine to lake in the East Antarctic margin. This project will provide essential data on AIS change since the last interglacial period

Regional sea-level highstand triggered Holocene ice sheet thinning across coastal Dronning Maud Land, East Antarctica

The East Antarctic Ice Sheet stores a vast amount of freshwater, which makes it the single largest potential contributor to future sea-level rise. However, the lack of well-constrained geological records of past ice sheet changes impedes model validation, hampers mass balance estimates, and inhibits examination of ice loss mechanisms. Here we identify rapid ice-sheet thinning in coastal Dronning Maud Land from Early to Middle Holocene (9000–5000 years ago) using a deglacial chronology based on in situ cosmogenic nuclide surface exposure dates from central Dronning Maud Land, in concert with numerical simulations of regional and continental ice-sheet evolution. Regional sea-level changes reproduced from our refined ice-load history show a highstand at 9000–8000 years ago. We propose that sea-level rise and a concomitant influx of warmer Circumpolar Deep Water triggered ice shelf breakup via the marine ice sheet instability mechanism, which led to rapid thinning of upstream coastal ice sheet sectors