Variations in mineralogy of dust in an ice core obtained from northwestern Greenland over the past 100 years

Abstract

Abstract. Our study is the first to demonstrate a\nhigh-temporal-resolution record of mineral composition in a Greenland ice\ncore over the past 100\xa0years. To reconstruct past variations in the sources\nand transportation processes of mineral dust in northwestern Greenland, we\nanalysed the morphology and mineralogical composition of dust in the SIGMA-D\nice core from 1915 to 2013 using scanning electron microscopy (SEM) and\nenergy-dispersive X-ray spectroscopy (EDS). The results revealed that the\nice core dust consisted mainly of silicate minerals and that the composition\nvaried substantially on multi-decadal and inter-decadal scales, suggesting\nthat the ice core minerals originated from different geological sources in\ndifferent periods during the past 100\xa0years. The multi-decadal variation\ntrend differed among mineral types. Kaolinite, which generally formed in\nwarm and humid climatic zones, was abundant in colder periods (1950–2004),\nwhereas mica, chlorite, feldspars, mafic minerals, and quartz, which\nformed in arid, high-latitude, and local areas, were abundant in warmer\nperiods (1915–1949 and 2005–2013). Comparison to Greenland surface\ntemperature records indicates that multi-decadal variation in the relative\nabundance of these minerals was likely affected by local temperature changes\nin Greenland. Trajectory analysis shows that the minerals were transported\nmainly from the western coast of Greenland in the two warming periods, which\nwas likely due to an increase in dust sourced from local ice-free areas as a\nresult of shorter snow/ice cover duration in the Greenland coastal region\nduring the melt season caused by recent warming. Meanwhile, ancient deposits\nin northern Canada, which were formed in past warmer climates, seem to be the\nbest candidate during the colder period (1950–2004). Our results suggest\nthat SEM–EDS analysis can detect variations in ice core dust sources during\nrecent periods of low dust concentration.\n