[A-CC37] [EJ] アイスコアと古環境変動

[ACC37-P05] A 60-year record of atmospheric sulfate and nitrate depositions preserved in the high-accumulation dome ice core, South East Greenland

*飯塚 芳徳¹、藤田 耕史²、服部 祥平³、植村 立⁴、関 宰¹、宮本 千尋⁵、鈴木 利孝⁶、吉田 尚弘^3,7、本山 秀明⁸、的場 澄人¹ (1.北海道大学低温科学研究所、2.名古屋大学大学院環境学研究科、3.東京工業大学物質理工学院応用化学系、4.琉球大学理学部、5.東京大学大学院理学系研究科、6.山形大学理学部、7.東京工業大学地球生命研究所、8.国立極地研究所)

キーワード：Greenland, ice core, sulfate ion, nitrate ion, Anthropogenic emission

Southeastern Greenland has a dome whose elevation is higher than 3000 m a.s.l. with high accumulation rate (about 1 m yr^-1) in water equivalent, which is suitable conditions for reconstructing past environmental changes with a high-time resolution. In this study, we measured major ion fluxes in 90 m ice core drilled from the SE-Dome region in 2015, and obtained records of annual ion fluxes from 1957 to 2014. High average NO₃^- flux (68.9 mg m^-2 yr^-1) with low δ¹⁵N value in the SE-Dome ice core suggests negligible effect of the post depositional NO₃^- loss. Thus, the SE-Dome region is one of the best locations for reconstructing nitrate fluxes. Decreasing trend of non-sea-salt (nss) SO₄^2- flux from 1970 to 2010 follows well that of anthropogenic SOx emission from North America, suggesting that the SO₄^2- flux in SE-Dome ice core mainly records anthropogenic emission of SOx from North America. In contrast, the decadal trend of NO₃^- flux in SE-Dome ice core differs from the decreasing trend of anthropogenic NOx emission in North America. The exact cause of the apparent non-linear relationship remains unclear but a formation of ammonium nitrate particles enhanced by SOx reduction appears to be an important mechanism as suggested by excess ammonium flux over sulfate. Our NO₃^- flux record is similar to other ice cores in Greenland high elevation sites on 5-yr running average, suggesting that NO₃^- concentrations records from these ice cores are reliable.