Место издания:International Union of Geodesy and Geophysics IUGG2003 Local Organizing Committee Sapporo
Первая страница:JSM15/07P/D-006 (p. B.85)
Аннотация:Changes in the shape of snow during metamorphism are observed until now at discrete time-steps, without the possibility to follow the changes of the microstructure within the multi-element crystals. We used x-ray computed tomography at a high spatial resolution (40 µm) and time steps of 8 hours to visualize the changes in crystal morphology. The insulated measurement chamber contains a snow sample of 50 mm diameter and variable height from 20-60 mm. Because a controlled temperature gradient can be produced in the measurement chamber we are able to determine at the same time the effective thermal conductivity. We developed a method to visualize and calculate the changes in the surface, and by that the effective sublimation and re-sublimation at the level of single microstructural units can be measured. Our preliminary results show that the rate of sublimation and re-sublimation is higher than estimated on classical grain size measurement, because the crystals growth seems not to be a steady process, but the grains undergo within a relatively short time span several sublimation-resublimation phases.