Grain Growth in Polycrystalline Fine-grained Ice Ih
Abstract
Deformation and flow of polycrystalline ice crystals in ice sheets and glaciers depends strongly on crystal size and temperature. In order to help understand grain-size effects on flow, we performed laboratory experiments on fine-grained, polycrystalline ice Ih samples to investigate the effect of temperature on the rate of grain growth in statically annealed ice. Fine-grained (5-8 mm) ice disks (25mm in diameter x 5 mm thick) were encapsulated and then annealed in a low-temperature bath of oil at ambient pressure. Temperature was varied from 230-240K. Ice samples were placed inside the bath for 1-75 hours to examine the effect of time and temperature on grain growth, grain-size distribution, and grain orientation. Low-temperature scanning electron microscopy (SEM) was used to measure grain size and growth. Neutron scattering is proposed for quantitative textural analysis and examination of the qualitative preferred crystallographic orientations deformed samples. SEM examination revealed grain growth at 234K, while at 230K samples appeared the same as starting material after 18 hours in the bath, showing no growth. Two samples annealed for 1 hour and 18 hours at 234 K showed strong grain growth with equant grain shape and distribution. Samples annealed at 235K revealed significant grain growth after 1 hour, with grain size nearly doubling after 75 hours. The results are significant in establishing grain growth rates under ambient conditions and temperatures applicable to natural ice settings, such as in glaciers and ice sheets. If changes in grain size occur at depth in natural ice bodies, such changes can significantly alter the nature of ice sheet rheology and glacial flow.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFM.C62A0911M
- Keywords:
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- 3900 MINERAL PHYSICS;
- 3902 Creep and deformation