[ACC26-P02] Variations in mineralogy of dust in the Greenland SIGMA-D ice core over the past 100 years using SEM
Keywords:mineral dust, ice core, Greenland , SEM
The ice core was drilled at the SIGMA-D site (N77°64’, W59°12’ ) of 2100 m a.s.l. in 2014. The length is 222.72 m and the estimated age at 113 m depth is 350 years before present . The ice samples were collected every five years in plastic bottles and freeze dried on a polycarbonate filter to concentrate micro-particles. Then, the filter was coated with platinum (Pt) for SEM analysis. Here we report the temporal variations in size distributions and compositions of the minerals during the past 100 years (A.D 1920-2013).
The SEM observation revealed that the mean size of mineral dust in the SIGMA-D ice core ranged from 1-3μm, which is similar to that of the other Greenland ice core dust that seems to be derived from distant areas. This suggests that the SIGMA-D ice core contained mainly long–range transported wind-blown mineral dust.
The EDS analysis revealed the ice core contained mainly silicate minerals, especially clay minerals that showed compositional variation among the samples. For example, the mineralogical composition varied in every 10-15 years and showed a negative correlation between minerals formed by chemical and physical weathering (kaolinite vs illite/micas and chlorite). This indicates that minerals in the ice core were derived from multiple geological sources and the source areas might have varied temporally. Furthermore, quartz and feldspar, which had larger particles than clay minerals and thus were generally used as a short-distant transport, were higher in 1920-1945 and 1990-2013 compared with the other periods. Based on the past temperature record in Greenland, the warming occurred from 1910 to 1945 and after 1990. This may suggest that the minerals were derived not only from distant areas but also from local sources, such as moraine around the ice sheet margin in warmer periods. This is likely due to exposure of ground surface without snow cover.