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Microstructural Evolution Of Fine-Grained Layers Through The Firn Column At Summit, Greenland, R. Lomonaco, M. Albert, I. Baker
Microstructural Evolution Of Fine-Grained Layers Through The Firn Column At Summit, Greenland, R. Lomonaco, M. Albert, I. Baker
Dartmouth Scholarship
We present a microstructural characterization of fine-grained layers from the top 90 m of firn from Summit, Greenland, performed using a combination of scanning electron microscopy techniques including secondary electron imaging, energy-dispersive spectroscopy and electron backscattered patterns, and X-ray microcomputed tomography. The impurities in the firn, both soluble impurities and dust particles, were found largely in the grain interiors. Both c- and a-axis pole figures do not show strong evidence of a preferred orientation of the grains even at the bottom of the firn column. The firn structure became increasingly anisotropic with vertical alignment in the top 3 m, probably …
A New Technique For Firn Grain-Size Measurement Using Sem Image Analysis, N.E. Spaulding, D.A. Meese, I. Baker, P.A. Mayewski
A New Technique For Firn Grain-Size Measurement Using Sem Image Analysis, N.E. Spaulding, D.A. Meese, I. Baker, P.A. Mayewski
Dartmouth Scholarship
Firn microstructure is accurately characterized using images obtained from scanning electron microscopy (SEM). Visibly etched grain boundaries within images are used to create a skeleton outline of the microstructure. A pixel-counting utility is applied to the outline to determine grain area. Firn grain sizes calculated using the technique described here are compared to those calculated using the techniques of Gow (1969) and Gay and Weiss (1999) on samples of the same material, and are found to be substantially smaller. The differences in grain size between the techniques are attributed to sampling deficiencies (e.g. the inclusion of pore filler in the …
Sem/Eds Observations Of Impurities In Polar Ice: Artifacts Or Not?, Ian Baker, Daniel Cullen
Sem/Eds Observations Of Impurities In Polar Ice: Artifacts Or Not?, Ian Baker, Daniel Cullen
Dartmouth Scholarship
A series of experiments was undertaken to determine the origin of filaments found in grain boundaries and impurity spots found in grain interiors of polar ice during observation in the scanning electron microscope. It is shown that although the filaments are artifacts, they demonstrate the presence of impurities segregated to the grain boundary planes. It is also demonstrated that the impurities observed in the grain interior reside there and were not transported from the grain boundaries during specimen preparation or observation.