Unclassified 



Security Classification 



DOCUMENT CONTROL DATA - R&D 



(Security ctaasitlcation ol title, body ol abstract and index/ng annofadon mus( be entered when the overall report is clessilied) 



1 ORIGINATIN G ACTIVITY fCorporale author) 



U. S. Naval Civil Engineering Laboratory 

 Port Hueneme, California 93041 



REPORT SECURI TV CLASSIFICi 



Unclassified 



2b GROUP 



3 REPORT TITLE 



Crystallographic Studies of Sea Ice in McMurdo Sound, Antarctica 



« DESCRIPTIVE NOTES (Type ol roporl and inclusive dates) 



Not final; October 1965 - June 1966 



5 AUTHORfS; (Last name, first name, initial) 



Paige, R. A. 



6 REPO RT DATE 



November 1966 



8a CONTRACT OR GRANT NO. 



b. PROJECT NO. Y-F015-1 1-01-026 



rOTAl. NO. OF PAGES 



35 



7b. NO OF REFS 



23 



9a ORIGINATOR'S REPORT NUMBERC^; 



TR-494 



10 AVAILABILITY/LIMITATION NOTICES 



Distribution of this document is unlimited. 



Copies available at the Clearinghouse (CFSTI) $2.00. 



11. SUPPLEMENTARY NOTES 



12 SPONSORING MILITARY ACTIVITY 



Naval Facilities Engineering Command 



13 ABSTRACT 



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. The number 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. 



DD 



1473 



0101-807-6800 



Unclassified 



Security Classification 



