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ILLUSTRATIONS 



Wenner method of dc resistivity measurements 

 Schematics of equipment layout on ice sheet (1954) 

 Schematics of equipment layout on ice sheet (1955) 

 Density profile of ice sheet, site No. 1 (1955) 

 Sea-ice salinity profiles 



Temperature profiles through ice and snow 

 Crystal grain size distribution for various ice samples 

 Air-bubble size distribution for various ice samples 

 Conducted heat flow through snow-covered ice sheet 



TABLES 



Seismic data taken in 1954 



Longitudinal plate-wave velocity data taken in 1955 



Ice thickness calculated from seismic method vs measured ice thickness, 1955 



Resonant rod measurements of sea ice, 1955 



Apparent dc resistivity measurements 



INTRODUCTION 



A knowledge of the physics of sea ice is essential to arctic naval operations. The 

 measurements reported here are one phase of a major continuing study being con- 

 ducted by the Navy Electronics Laboratory to furnish geophysical data on the 

 arctic regions which will be of value in naval operations in that area. 



A survey of the literature^'^'^ (see References at end of report) in 1953, con- 

 cerning the longitudinal plate-wave velocity in fresh-water ice, showed a signifi- 

 cant variation in velocity. At that time there were no data on longitudinal plate- 

 wave velocities in sea ice; however, since that time one article on the subject has 

 been published,* indicating that if variations existed in the longitudinal plate- 

 wave velocity in sea ice, these variations would be related to certain physical 

 properties of the ice. 



During the Winter 1954 Bering Sea Expedition and the Winter 1955 Bering 

 Sea Expedition, measurements were made of the longitudinal plate-wave velocity. 

 In 1954, the location of the ice sheet in which measurements were made was 

 60°20'N, 168°38'W; and in 1955 the ice sheet, although variable in position 

 during the several days measurements were being made, occupied the position 

 63°05'N, 166°09' W. In 1955, in addition to the measurement of the longitudinal 

 plate- wave velocity, other physical properties of the ice which might be of sci- 

 entific interest were measured. The investigation of other sea-ice parameters in- 

 cluded: (1) sampling profiles of density, temperature, salinity, air bubble, and 

 crystal grain; (2) measurement of the longitudinal wave velocity in ice rods; 

 (3) measurement of the frequency of air-coupled flexural waves to determine ice 

 thickness; and (4) resistivity measurements. 



The information obtained from these two surveys represents point data; that is, 

 data which were taken at a given point in a relatively short time interval. 



