[A-CC26] アイスコアと古環境モデリング

[ACC26-P03] グリーンランドアイスコアから復元する過去100年の鉱物ダスト起源変動と空間分布

*永塚 尚子¹、東 久美子^1,2、對馬 あかね³、藤田 耕史⁴、的場 澄人⁵、大沼 友貴彦⁶、小室 悠紀⁷、平林 幹啓¹、尾形 純¹、塚川 佳美¹、北村 享太郎¹、青木 輝夫^1,2、Popp Trevor James⁸、Dahl-Jensen Dorthe⁸ (1.国立極地研究所、2.総合研究大学院大学、3.千葉大学理学研究院、4.名古屋大学環境学研究科、5.北海道大学低温科学研究所、6.宇宙航空研究開発機構、7.富士山環境研究センター、8.コペンハーゲン大学)

キーワード：鉱物ダスト、アイスコア、グリーンランド、SEM-EDS分析

To reconstruct past variations in the sources and transportation processes of mineral dust in northwestern Greenland, we analyzed the morphology and mineralogical composition of dust in the SIGMA-D ice core (77.64N, 59.12W, 2100 m a.s.l) from 1915 to 2013 using scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results revealed that the ice core dust consisted mainly of silicate minerals and that the composition varied substantially on multi-decadal and inter-decadal scales, suggesting that the ice core minerals originated from different geological sources in different periods during the past 100 years. The multi-decadal variation trend differed among mineral types. Kaolinite, which generally formed in warm and humid climatic zones, was abundant in colder periods (1950–2004), whereas mica, chlorite, feldspars, mafic minerals, and quartz, which formed in arid, high-latitude, and local areas, were abundant in warmer periods (1915–1949 and 2005–2013). Comparison to Greenland surface temperature records indicates that multi-decadal variation in the relative abundance of these minerals was likely affected by local temperature changes in Greenland. Trajectory analysis shows that the minerals were transported mainly from its west coast during the two warming periods. This was likely due to an increase in dust sourced from ice-free areas as a result of shorter snow/ice cover duration in the Greenland coastal region during the melt season caused by recent warming. Meanwhile, ancient deposits in northern Canada, which were formed in past warmer climates, seem to be the best candidate during the colder period (1950–2004). Our results suggest that SEM-EDS analysis can detect variations in ice core dust sources during recent periods of low dust concentration [1].
To reveal spatial variation in the sources of minerals on the Greenland ice sheet, we have also analyzed dust from the northeastern Greenland ice core (EGRIP: 75.62N, 35.96W, 2708 m a.s.l) during the past 100 years. The results showed that the particle size, mineral composition, and compositional variations of the EGRIP ice core dust differed significantly from those of the SIGMA-D, indicating that the sources and transport processes of the minerals were different between the two ice cores. The detailed discussion will be presented at the symposium.