JpGU-AGU Joint Meeting 2017

Presentation information

[EJ] Oral

A (Atmospheric and Hydrospheric Sciences) » A-CC Cryospheric Sciences & Cold District Environment

[A-CC37] [EJ] Ice cores and past environmental changes

Tue. May 23, 2017 3:30 PM - 5:00 PM A08 (Tokyo Bay Makuhari Hall)

convener:Kenji Kawamura(National Institute of Polar Research, Research Organization of Information and Systems), Nozomu Takeuchi(Chiba University), Ayako Abe-Ouchi(Atmosphere and Ocean Research Institute, The University of Tokyo), Chairperson:Akane Tsushima(Research Institute for Humanity and Nature)

4:00 PM - 4:15 PM

[ACC37-13] On the possibility of radiometric dating on the “oldest ice” using cosmogenic 26Al/10Be ratio: Insights from the Dome Fuji second deep (DF2) ice core

*Kazuho Horiuchi1, Tomoko Uchida2, Ai Sugawara1, Shoko Seino1, Saya Matsuda1, Hiroyuki Matsuzaki3, Hideaki Motoyama4 (1.Graduate School of Science and Technology, Hirosaki University, 2.Institute of Geology and Paleontology, Tohoku University, 3.MALT, The University of Tokyo, 4.National Institute of Polar Research)

Deep ice core records have been playing a crucial role in paleooclimatology. However, there are no records that have reached over ca. 800 ka. To overcome this problem, several research groups are planning to recover the “oldest ice” (~1.5 Ma) from near the bases of ice-sheets overlying inland Antarctica (see e.g. Schiermeier, 2016). Nevertheless, it may be not an easy task to obtain an accurate chronology from such deepest parts of ice cores, because layer inclination and/or folding may prevent us to construct accurate stable-isotope chronologies, which usually rely on normal stratigraphy.

Cosmogenic 26Al and 10Be are produced by interactions of comic rays with specific elements in the atmosphere. Because the atmospheric production is similar between 26Al and 10Be, an exponential decrease of the 26Al/10Be ratio with time, in ordinary cases, should represents the difference of the decay constants of the nuclides (T1/2 of the 26Al/10Be ratio is 1.45 Myr). In this presentation, we show the profiles of the 26Al/10Be ratios of certain stratigraphic intervals of the Dome Fuji second deep (DF2) ice core, plotted against the latest age model for this core (Dome Fuji ice core project members, 2017). By investigating these data, we discuss about the possibility of the radiometric dating on the “oldest ice” of an age of up to 1.5 Ma.