Imaging and characterizing fresh and metamorphosed snow crystals with low temperature scanning electron microscopy

TitleImaging and characterizing fresh and metamorphosed snow crystals with low temperature scanning electron microscopy
Publication TypeJournal Article
Year of Publication2003
AuthorsW.P. W, A. R, J. F, E.G. J, , C. P
JournalRecent Research Developments in Geophysics
Volume5
Start Page21
Pagination21-55
Date Published10/2003
ARIS Log Number149819
Keywordsmicroscopy, scanning, snow crystals
Abstract

A technique known as low temperature scanning electron microscopy (SEM) has been used to image precipitating and metamorphosed snow crystals, as well as glacial ice. This review summarizes the methods used to collect, transport and store samples of snow and ice and illustrates the basic types of snow crystals that occur in nature along with the changes they undergo in snowpack. In addition, the study illustrates firn and glacial ice which were also sampled and examined with the low temperature SEM. The results illustrate the ease and the resolution with which samples of snow and ice can be observed, studied and photographed. Until recently, studies of snow and ice were largely restricted to a hand lens or the light microscopy (LM); the laboratory and the instrumentation had to be cooled to temperatures below freezing, frequently near a collection site. This expensive and inconvenient requirement is not necessary for observations using the low temperature SEM. Alternatively, samples are easily collected in the field and have been shipped to the electron microscopy laboratory by common air carrier from distances as far away as 8,000 km. Delicate specimens of snow crystals and ice grains survive the shipment procedures and have been stored for as long as 3 years without undergoing any structural changes. Furthermore, the tilting stage of the SEM permits photographs to be recorded that contain the information necessary for three-dimensional imaging. As a result, visualization of the true shapes of snowflakes, snow crystals, snow clusters, ice grains and their interspersed air spaces is easily achieved.

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