Advanced electron microscopy techniques for studying ice and firn cores

For many years, the microstructural characterization of ice and firn has used optical microscopy often involving observation of thin sections between crossed polarizers. However, such an approach, in addition to being of low resolution, does not provide complete information on the microstructure. In previous work (Obbard et al. 2003), we have shown how scanning electron microscopy coupled with X-ray microanalysis can be used to determine the microstructural location of impurities in ice cores. In this paper, we outline the use of scanning electron microscopybased techniques to determine the 3-D orientation of grains and, thus, enable more complete analysis of the orientation relationships between grains in ice and firn. In addition, we show how scanning electron microscopy can be used to determine the internal surface area, porosity and grain size in firn.