CRYSTALLOGRAPHIC STUDIES OF SEA ICE IN MCMURDO SOUND, ANTARCTICA.
NAVAL CIVIL ENGINEERING LAB PORT HUENEME CALIF
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The sea ice in McMurdo Sound is used extensively for aircraft operations, travel, and docking areas. The safety and efficiency of utilizing the sea ice depends upon many factors affecting its physical properties throughout the season. Sea ice is a crystalline solid with physical properties that are highly temperature dependent between -1.8 C and -10 C. This dependence becomes less with decreasing temperatures. A study of various crystal parameters and structure is essential for a better understanding of their relationship with strength properties. Horizontal banding in the ice sheet was studied to determine the effect of temperature fluctuations on band frequency. Various crystal parameters such as subcrystal platelet width, crystal length-to-width ratios, and crystal size were measured from photographs of thin sections. Subcrystal platelet width increased with depth from about 0.5 mm at the surface to about 1 mm at 2.8 meters. The length-width ratio of single crystals increased from 2 to 1 near the surface to more than 5 to 1 at depths greater than 2 meters. Thenumber of crystals per unit area decreased with depth. Strained ice from a pressure ridge showed preferred c-axis orientation and wavy extinction similar to that observed in strained quartz. There is apparently no correlation between strength and crystal structure in a mature isothermal ice sheet. Author
- Snow, Ice and Permafrost