[A-CC29] Ice cores and paleoenvironmental modeling

[ACC29-02] Overview and recent activities for shallow ice core project on a high-accumulation dome, southeast Greenland

★Invited Papers

*Iizuka Yoshinori¹, Sumito Matoba¹, Ryoto Furukawa¹, Takuto Ando¹, Takeshi Saito¹, Fahmida Parvin¹, Tomomi Amino¹, Mai Shibata¹, Moe Kadota¹, Osamu Seki¹, Shin Sugiyama¹, Ryu Uemura², Koji Fujita³, Asuka Tsuruta⁴, Shohei Hattori⁴, Shuji Fujita⁵, Hideaki Motoyama⁵, Naoko Nagatsuka⁵, Ikumi Oyabu⁵, Satoru Yamaguchi⁶, Satoshi Adachi⁶, Hiroshi Ohno⁷, Akira Hori⁷, Chihiro Miyamoto⁸, Yoshio Takahashi⁸, Chiaki Sasaki⁹, Toshitaka Suzuki⁹, Angel T. Bautista VII^10,11, Hiroyuki Matsuzaki¹⁰, Kazuho Horiuchi¹², Atsushi Miyamoto¹³, Kei Yoshimura¹⁴, Jesper Sjolte¹⁵, Masashi Niwano¹⁶, Naga Oshima¹⁶, Akihiro Hashimoto¹⁶, Tetsuhide Yamasaki¹⁷, Teruo Aoki¹⁸ (1.Institite of Low Temperature Science, Hokkaido University, 2.Department of Chemistry, Biology, and Marine Science, Faculty of Science, University of the Ryukyus, 3.Graduate School of Environmental Studies, Nagoya University, 4.Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, 5.National Institute of Polar Research, 6.The National Research Institute for Earth Science and Disaster Prevention, 7.Department of Civil and Environmental Engineering, Kitami Institute of Technology, Hokkaido, Japan, 8.Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 9.Faculty of Science, Yamagata University, 10.Department of Nuclear Engineering and Management, The University of Tokyo, 11.Philippine Nuclear Research Institute - Department of Science and Technology (PNRI-DOST), 12.Graduate School of Science and Technology, Hirosaki University, 13.Institute for the Advancement of Higher Education, Hokkaido University, 14.Institute of Industrial Science, The University of Tokyo, 15.Department of Geology, Quaternary Science, Lund University, 16.Meteorological Research Institute, Japan Meteorological Agency, 17.Avangnaq, 18.Graduate School of Natural Science and Technology, Okayama University)

Keywords:ice core, Greenland, high accumulation

On May 2015, we drilled a 90.45 m ice core in a high accumulation area of the southeastern Greenland Ice Sheet. The drilling site (SE-Dome; 67.18°N, 36.37°W, 3170 m a.s.l.) is located 185 km north of the town of Tasiilaq in southeastern Greenland [1]. Then we measure physical and chemical properties of the SE-Dome ice core. Based on the measurements, we show the general characteristics of the SE-Dome ice core. I) As for dating of the ice core [2], we propose a dating method based on matching the δ¹⁸O variations between ice-core records and records simulated by isotope-enabled climate models. We applied this method to a δ¹⁸O record from the SE-Dome ice core. The close similarity between the δ¹⁸O records from the ice core and models enables correlation and the production of a precise age scale, with an accuracy of a few months. II) As for physical property [3], the ice was –20.9 ºC at 20-m depth. The close-off density of 830 kg m^-3 occurs at 83.4–86.8-m depth, which is about 20-m shallower than that obtained from empirical models, indicating that the firn with a higher density is softer than that from empirical result. We interpret that the high accumulation rate creates a high overburden pressure in a short time. The relative softness of the firn may arise from 1) there being not enough time to form bonds between grains as strong as those in a lower accumulation-rate area, and similarly, 2) the dislocation density in the firn being relatively high. III) As for chemical property [4], we measured the major ion fluxes, and obtained records of annual ion fluxes from 1957 to 2014. We find a high average NO₃^- flux (1.13 mmol m^-2 yr^-1) in the ice core, which suggests a negligible effect from post-depositional NO₃^- loss, indicating the SE-Dome region is an excellent location for reconstructing nitrate fluxes. For the non-sea-salt (nss) SO₄^2- and NH₄⁺ fluxes, a decreasing and increasing trend from 1970 to 2010, respectively, tracks well with the anthropogenic SO_x and NH₃ emissions. In contrast, the decadal trend of NO₃^- flux differs from the decreasing trend of anthropogenic NO_x emissions. We continue to investigate the paleoenvironment with multi proxies from several analyses (e.g. [5]) of the high-time-resolution and chemicals-well-preserved ice core.

References
[1] Iizuka et al., (2016). Bulletin of Glaciological Research, 34, 1–10. https://doi.org/10.5331/bgr.15R03
[2] Furukawa et al., (2017). Journal of Geophysical Research: Atmospheres, 122, 10,873–10,887. https://doi.org/10.1002/2017JD026716
[3] Iizuka et al., (2017). Arctic, Antarctic, and Alpine Research, 49, 13–27. https://doi.org/10.1657/AAAR0016-034
[4] Iizuka et al., (2018). Journal of Geophysical Research: Atmospheres, 123. https://doi.org/10.1002/2017JD026733
[5] Bautista et al., (2018) Journal of Environmental Radioactivity 184–185, 14–21, https://doi.org/10.1016/j.jenvrad.2017.12.015