A technique for the examination of polar ice using scanning electron microscopy

British Antarctic Survey, Cambridge, England, United Kingdom
Journal of Microscopy (Impact Factor: 2.33). 03/2002; 205(Pt 2):118-24. DOI: 10.1046/j.0022-2720.2001.00981.x
Source: PubMed


The microstructure and location of impurities in polar ice are of great relevance to ice core studies. We describe a reliable method to examine ice in the scanning electron microscope (SEM). Specimens were cut in a cold room and could have their surfaces altered by sublimation either before (pre-etching) or after (etching) introduction to the cryo-chamber of the SEM. Pre-etching was used to smooth surfaces, whilst etching stripped away layers from the specimen surface, aiding the location of particles in situ, and allowing embedded structures to be revealed. X-ray analysis was used to determine the composition of localized impurities, which in some cases had been concentrated on the surface by etching. Examining uncoated surfaces was found to be advantageous and did not detract from qualitative X-ray analysis. Imaging uncoated was performed at low accelerating voltages and probe currents to avoid problems of surface charging.

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Available from: Piers R. F. Barnes, Jun 09, 2015
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    • "These pressure– temperature conditions are in the water vapour field and ice is unstable and sublimes. The rate of sublimation is estimated to be about 0.5 µm min −1 at −100 • C and >1 µm min −1 at >–90 • C (Davy & Branton, 1970; Barnes et al., 2002; Waller et al., 2005). This sublimation rate would cause a loss of about 50 to 500 µm, respectively, from the sample surface over an 8–9 h period, which is typically the timescale required to characterize subgrain boundaries in a 1 cm 2 ice sample using EBSD. "
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    • "Wolff and Paren [12] suggested that the DC conductivity of polar ice could be due to the presence of liquid layers at the grain boundaries. In agreement with this idea, SEM-EDS studies have surmised the presence of sulfuric acid at the grain boundaries in Antarctic ice [13] [14] [15], and Fukazawa et al. [16] have found evidence for sulfuric acid at the triple junction of South Yamato and Nansen ice cores, Antarctica by micro-Raman spectroscopy . Rempel et al. [17] [18] suggested that the ions exist as acid solutions (sulfuric and nitric acid) displaced by premelting and anomalous diffusion through the vein network. "
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