Direct observation of salts as micro-inclusions in the Greenland GRIP ice core

Abstract

Abstract We provide the first direct evidence that a number of water-soluble compounds, in particular calcium sulfate (CaSO 4 ·2H 2 O) and calcium carbonate (CaCO 3 ), 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. CaSO 4 ·2H 2 O is found in abundance throughout the Holocene and the last glacial period, while CaCO 3 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.