[A-CC29] Ice cores and paleoenvironmental modeling

[ACC29-10] Variations in mineralogy of dust in ice cores obtained from northwestern and northeastern Greenland over the past 100 years

★Invited Papers

*Naoko Nagatsuka¹, Kumiko Goto-Azuma^1,2, Akane Tsushima³, Koji Fujita⁴, Sumito Matoba⁵, Yukihiko Onuma⁶, Yuki Komuro¹, Motohiro Hirabayashi¹, Jun Ogata¹, Yoshimi Tsukagawa¹, Kyotaro Kitamura¹, Teruo Aoki^1,2, Trevor James Popp⁷, Dorthe Dahl-Jensen⁷ (1.National Institute of Polar Research, 2.SOKENDAI, 3.Graduate School of Science, Chiba University, 4.Graduate School of Environmental Studies, Nagoya University, 5.Institute of Low Temperature Science, Hokkaido University, 6.Institute of Industrial Science, University of Tokyo, 7.University of Copenhagen)

Keywords:mineral dust, ice core, SEM-EDS analysis, Greenland

To reconstruct past variations in the sources and transportation processes of mineral dust in northwestern Greenland, we analysed 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 microscopy (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 the western coast of Greenland in the two warming periods, which was likely due to an increase in dust sourced from local 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.
To reveal spatial variation in the mineral dust morphology and composition in the Greenland Ice Sheet, we have also analyzed the dust from northeastern Greenland ice core (EGRIP: 75.62N, 35.96W, 2708 m a.s.l) during the past 100 years. The results will be presented at the meeting.