[A-CC33] アイスコアと古環境モデリング

[ACC33-06] 多チャンネル高解像度VHFレーダーシステムを用いた新しいアイスコア掘削地点の調査

*津滝 俊^1,2、藤田 秀二^1,2、川村 賢二^1,2,3、阿部 彩子^4,1、Brice Liefferinge⁵、松岡 健一⁵、Prasad Gogineni⁶、David Braaten⁷、John Paden⁷、Fernando Rodriguez-Morales⁷、Jean-Charles Gallet⁵ (1.国立極地研究所、2.総合研究大学院大学、3.海洋研究開発機構、4.東京大学大気海洋研究所、5.ノルウェー極地研究所、6.アラバマ大学、7.カンザス大学)

キーワード：第3期ドームふじ観測計画、アイスレーダ、南極氷床、南極地域観測隊

Knowledge gained from ice core studies is crucial to understand the past and present climate and to predict the impacts of future climate changes. The International Partnership for Ice Core Sciences (IPICS) identified that drilling deep ice cores extending back in time to 1.5 million years (Ma) is crucial to better understand the change of the periodicity of the glacial cycles from 40 thousand years (ka) to the current 100 ka during the mid-Pleistocene transition (0.9−1.2 Ma). At the Little Dome C site in Antarctica, the Beyond EPICA project obtained an ice core with a chronological record spanning over 1.2 Ma. The Dome Fuji area in East Antarctica is one of the candidate areas where we may be able to find very old ice near the bottom of the ice sheet. The Japanese Antarctic Research Expedition (JARE) has conducted deep ice corings at Dome Fuji twice in the past decades. They recovered ice cores covering ages up to about 720 ka BP. To obtain the oldest ice core, it is crucial to ensure that the ice sheet base remains frozen for an extended period and that the ice stratigraphy near the base remains undisturbed. Additionally, achieving sufficient age resolution requires maintaining an appropriate ice thickness to prevent basal melting from geothermal heat. High-sensitivity ice-penetrating radar is essential for reducing uncertainties in parameters such as ice thickness and geothermal heat flux, as well as for accurately evaluating englacial and subglacial conditions.

We conducted a radar survey at Dome Fuji in the 2018−2019 season as a collaboration between The University of Kansas, The University of Alabama, National Institute of Polar Research (Japan), Norwegian Polar Institute and The University of Tokyo. We used a multi-channel high-resolution very high frequency (VHF) radar operating in the frequency range of 170–230 MHz developed by CReSIS, University of Kansas for the data collection. We investigated 2,700 km in an area of about 1,000 km². The final spacing between the survey lines varied between 0.5 km and 0.25 km. This new instrument can detect reflectors in the near-basal region more clearly than previous surveys. We analyze the CReSIS radar data to construct an improved radar stratigraphy in the Dome Fuji area to foster the identification of a suitable drilling site in the region.