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SEA ICE PROBLEMS 



Clifford A. Barnes 



INTRODUCTION 



In dealing with sea ice, oceanographers are concerned primarily with 

 properties, processes and distribution. The properties may be physical, such 

 as acoustic, electromagnetic, optical, hardness, strength, crystal structure 

 and the like, chemical or geological. Processes include the interaction with 

 water, the atmosphere, other ice and the bottom or coast, freezing and melting, 

 disintegration and movement. The distribution involves arrangement, compact- 

 ness of cover, thickness, size, and surface and subsurface characteristics, all 

 of which change in space and time, necessitating both synoptic and climatic geo- 

 graphic pictures. 



The term "sea ice" is used herein to refer to any ice formed by the 

 freezing of sea water. Glacial ice formed on land, and river and lake ice dis- 

 charge into the sea in considerable amount. These ice types may drift great 

 distances at sea, but differ from true sea ice. In investigating the physical 

 properties of the different ice types and the response of ice to the oceanographic 

 and meteorological environment, much of the basic instrumentation is independ- 

 ent of the ice type. The drift rates of pack ice or of berg fragments before the 

 wind for example depends largely on the size, shape, orientation and grouping 

 of the individual pieces and little upon the chemical connposition of the ice. On 

 the other hand, sea ice is unique in being formed in saline solution and entrap- 

 ping appreciable amounts of salt. Investigating such problems as the freshen- 

 ing of ice on aging, or the changing of ion-ratios within the ice may require very 

 specialized instrumentation. 



Some question may be raised concerning the extent to which oceanography 

 is involved in sea ice studies, and to what extent the instrumentation used falls 

 into the category of oceanographic instrumentation. The formation, movement, 

 disintegration and many of the physical properties of sea ice are intimately re- 

 lated to conditions in the sea and lower atmosphere and involve particularly the 

 fields of oceanography and meteorology. Currents and the physical and chemi- 

 cal properties of the water mass limit the distribution of sea ice. These ocea- 

 nographic conditions are more or less directly influenced by the meteorological 

 conditions. The temperature reginne within sea ice and its thermal conductivity 

 may be almost exclusively a problem in physics, the structure of the ice crys- 

 tals one in geology, and the precipitation of salts during the freezing process 

 one in chemistry. In experimental work, the same instrumentation might well 

 be used regardless of whether or not the attack is primarily oceanographic. 

 Oceanographers have always borrowed heavily fronn the contributing or related 

 sciences and have done so in the case of instrumentation for sea ice studies. 

 Most of the instruments used have been developed for other purposes and adapt- 

 ed to sea ice studies, specialized instrumentation being held to a minimum. At 



