Section 43. Ice Under Ice 



The course of deep-ice formation underneath ice is characteristic. Large supplies of almost 

 fresh melt water form during melting on the surface of the ice fields and fast ice. After the ice 

 fields either melt through or are broken, this melt water goes under the ice and here, spreading 

 along the sea water, which at this time is near freezing, creates a peculiar ice under ice. This 

 phenomenon was first discovered by Nansen. He noted that ice which had formed in the autumn of 

 1893 attained a thickness of 257 cm. Six days later, Nansen discovered, completely unexpectedly, 

 that the thickness of the ice had increased 19 cm despite the fact that the surface of the ice melted 

 several centimeters daily. 



With further measuring, Nansen obtained the data given in table 26. 



TABLE 26. ICE THICKNESS ACCORDING TO NANSEN'S MEASUREMENTS 



Nansen explained this phenomenon by the fact that the fresh water formed during melting, 

 when draining off under ice, comes in contact with the saline sea water, whose temperature is -1.6°. 



It is natural that the fresh water which freezes at 0° quickly turns into a peculiar sponge ice 

 when coming into contact with the upper layer of the sea. 



Toll's Russian polar expedition of 1900 to 1903 investigated exhaustively the process of spring 

 ice-imder-ice growth both under natural and laboratory conditions. The observations of this expe- 

 dition supported Nansen's conclusions. As it developed, fresh-water ice under ice, formed as a 

 result of the contact between the drain-off of fresh snow water with the cold sea water (whose tem- 

 perature is from -1.2° to -1.5°), is an ice of coarsely crystalline form, which sometimes attains 

 a thickness of 10 to 15 cm. 



This phenomenon was checked in the laboratory. A piece of ice about 5 cm thick was placed 

 in a solution of table salt having a temperature of about -5°. Fresh water, treated with fuchsin 

 was added to the solution through a vertical hole in the piece of ice. 



Draining under the ice and coming in contact with the cold solution, the fresh water began to 

 freeze, and froze to the lower surface of the ice. In this manner, the phenomenon and structure of 

 "sub-ice, fresh-water ice, " which had been observed in nature, were reproduced exactly in the lab- 

 oratory. Sub-ice, fresh ice has a clear crystalline structure consisting of loosely connected large 

 crystals. Its lower surface is very irregular and coarse, and a layer of ice porridge consisting of 

 weakly joined ice crystals is ordinarily located under it. 



103 



