We provide the first direct evidence that a number of water-soluble compounds, in particular calcium sulfate (CaSO4 2H2O) and calcium carbonate (CaCO3), are present as solid, micron-sized inclusions within the Greenland GRIP ice core. The compounds are detected by two independent methods: micro-Raman spectroscopy of a solid ice sample, and energy-dispersive X-ray spectroscopy of individual inclusions remaining after sublimation. CaSO4 2H2O is found in abundance throughout the Holocene and the last glacial period, while CaCO3 exists mainly in the glacial period ice. We also present size and spatial distributions of the micro-inclusions. These results suggest that water-soluble aerosols in the GRIP ice core are dependable proxies for past atmospheric conditions.

The ion concentrations measured at each depth are averaged over five samples. Data extracted in the frame of a joint ICSTI/PANGAEA IPY effort, see http://doi.pangaea.de/10.1594/PANGAEA.150150

Supplement to: Sakurai, Toshimitsu; Iizuka, Yoshinori; Horikawa, Shinichiro; Johnsen, Sigfús Jóhann; Dahl-Jensen, Dorthe; Steffensen, Jørgen Peder; Hondoh, Takeo (2009): Direct observation of salts as micro-inclusions in the Greenland GRIP ice core. Journal of Glaciology, 55(193), 777-783