[M-IS05] 南大洋・南極氷床が駆動する全球気候変動

[MIS05-P10] Periods of local melt during the Holocene at Terre Adelie, East Antarctica revealed by beryllium isotope ratios

*Bethany Behrens^1,2、Yusuke Yokoyama^1,2,4,5、Yosuke Miyairi¹、Adam David Sproson¹、Masako Yamane³ (1.Atmosphere and Ocean Research Institute, University of Tokyo, Japan、2.Graduate Program on Environmental Science, University of Tokyo, Japan、3.Institute for Space-Earth Environmental Research, Nagoya University, Japan、4.Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo, Japan、5.Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Natsushimacho, Japan)

キーワード：Wilkes Subglacial Basin, East Antarctica, Beryllium isotopes, Holocene, Glacial retreat

The West Antarctic Ice Sheet (WAIS) and East Antarctic Ice Sheet (EAIS) contain an amount of ice equivalent to 3-5 m and 53 m sea level rise, respectively (1). The WAIS, as a largely marine-based ice sheet, is susceptible to changes in ocean temperatures and prone to retreat. Recent research has revealed that areas of the EAIS situated below sea level are also very sensitive to atmospheric and oceanic temperature changes and vulnerable to retreat (2, 3). The two largest subglacial basins in East Antarctica, the Wilkes and Aurora basins, hold a total ice mass equivalent to 28 m sea level rise (4), demonstrating that even a partial collapse of the EAIS would have a major effect on global sea level.



While we know the general timing of post-LGM glacial retreat around Antarctica, there is scarce data on specific locations with detailed, high-resolution records of ice sheet dynamics during the Holocene. Here we present reactive beryllium-10 and beryllium-9 ratio (¹⁰Be/⁹Be_reac) analysis of a marine sediment core from the Adélie Basin, located on the continental shelf offshore the Wilkes Basin. The sediment record covers the most recent period of major Holocene ice sheet retreat, sea level rise, and increased atmospheric CO₂ since the Last Glacial Maximum ice sheet retreat (5). The beryllium isotope data suggest oceanic or climatic changes occurred at ca. 9.9 ka and from ca. 4 ka BP. From prior research, we can conclude our high meteoric ¹⁰Be values at 9.9 ka BP are attributed to an open marine environment created by the retreat of grounded ice along with an increased influx of meltwater (6-8). The increasing concentration of reactive ¹⁰Be values starting from ~4 ka indicates a change in regime, possibly linked to changes in climate.



(1) Wilson DJ, Bertram RA, Needham EF, van de Flierdt T, Welsh KJ, McKay RM, et al. Nature. 2018;561(7723):383-6.

(2) Hansen MA, Passchier S. Geo-Marine Letters. 2017;37(3):207-13.

(3) DeConto RM, Pollard D. Nature. 2016;531:591.

(4) Shen Q, Wang H, Shum C, Jiang L, Hsu HT, Dong J. Scientific reports. 2018;8(1):4477.

(5) Yokoyama Y, Esat TM, Thompson WG, Thomas AL, Webster JM, Miyairi Y, et al. Nature. 2018;559(7715):603-7.

(6) Yokoyama Y, Anderson JB, Yamane M, Simkins LM, Miyairi Y, Yamazaki T, et al. Proceedings of the National Academy of Sciences. 2016;113(9):2354.

(7) Valletta RD, Willenbring JK, Passchier S, Elmi C. Paleoceanography and Paleoclimatology. 2018;33(9):934-44.

(8) Behrens B, Miyairi Y, Sproson AD, Yamane M, Yokoyama Y. Journal of Quaternary Science. 2019;34(8):603-8.