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ics and thermodynamics of sea ice. The work must be done in the laboratory 

 where the time, pressure and temperature functions are under control and 

 known. The studies should be on sufficient scale to work with the transient 

 phenomenon, as well as continuation of work with equilibrium states in calori- 

 meters. For example, perhaps dye tracers can show brine cell migration. 



From the laboratory, perhaps, will come a quantitative type description 

 of sea ice in terms of a set of equilibrium states and changes therefrom, with 

 variations of the intrinsic parameters, the temperature, the pressure, molal 

 ratios, etc. Without this, what further can be done in the field with the electri- 

 cal conductivity studies of Dichtel and Lundquist, except to just repeat their 

 nneasurements ? You find they did their work very neatly and well. 



Sea Ice Dynamics and Acoustics - In contrast, however, certain field studies 

 are needed; some because they will be the first measurements, others because 

 they will give extensive properties of the sea ice systenn. Considerable work 

 and techniques are being mastered by A. P. Crary and associates for the study 

 of propagation of flexural waves by the ice sheet and sound propagation in the 

 air above it. However, sound propagation in the sea beneath the ice has not 

 been studied; reflection and scattering coefficients are unknown even as to or- 

 der of magnitude. The instrumentation, but not the ships, can be borrowed 

 from propagation work in non-ice oceans. The need that the sending and re- 

 ceiving ships separate from each other over known and controlled distances, 

 points to the use of a submarine which can move under the sea ice. In addition, 

 the submarine is needed to measure the underside profile of the sea ice along 

 the transmission path. At low sound frequencies, the underside roughness 

 parameter of the sea ice should considerably influence reverberation and reflec- 

 tions along the transmission path. At high frequencies, the bubble distribution 

 and size within the sea ice are likely governing parameters. Whether a sub- 

 marine can carry out this task is a mute question. The Nautilus in 1933 pene- 

 trated under the ice one boat length, which hardly answers any questions. 



Though the instrumentation for sound transmission studies is available, 

 the vehicles, icebreaker and submarine, are strictly a naval problem both as to 

 availability and operating cost. Even one transmission run would tell a great 

 deal; however, a long, extended, set of measurements might add little more 

 unless taken in step with equations needed to describe the internal mechanics of 

 sea ice. 



Other field problems that can profitably be done now, concern sea ice 

 dynamics. During the recent winter expedition of the icebreaker, USS BURTON 

 ISLAND, we attempted to measure the force fields that must be present in sea 

 ice sheets when differential motions are taking place between parts of the ice 

 field. These are manifest by shearing of the ice sheet and the resulting rafting 

 or tenting. We had simple crusher gages in the form of various sized tin cans 

 which we buried. In addition, a heavy ribbed box was built with diaphragms for 

 walls. The diaphragm deformations were measured by strain gages in order to 

 record magnitude and time characteristics of pressure pulses that likely pass 

 through the ice sheet. However, I am sorry to report that during the entire 

 expedition, no rafting occurred in areas we could reach. The wind prevailed 

 from one direction; differential motions were not generated. This type of ice 

 dynamic study has yet to be done, and places the rather rugged requirements on 

 the vehicle that it be capable of living in the winter ice or that it must get the 

 men and equipment to the ice and maintain a camp thereon. 



Work has not been done on the shear strength or mechanics of shear and 

 crystalline fracture, though such studies are of high import to ship design. For 



