SCIENTIFIC RESULTS 11 



11) fouiul in the Arctic Ocean was 14.59 0/00, this beino- a sample 

 cut from a sheet of thin ice that had been exposed to the very low 

 temi)erature of about -40° C. (-40° F.). It is true that the ice 

 cover is continually l)ein<r rended apart ex})osino; the Avater to ex- 

 tremely fri<iid temperatures. But the total amount of the salty ice 

 tliiis prochiced is comi)aratively small, because in relatively few in- 

 stances does ice form under supercooled conditions. 



The two })i'incipal rerrions of ice formation in the Arctic Ocean 

 ai'e : 



{(') The siiallow waters of the Eurasian shelf and in the north- 

 ern Xortli American country. 



{/') The underside of the pei'manent polar ice cap. 



In the case of {(/) the sea surface normally becomes covered early 

 in the autumn before the atmosphere has greatly cooled, and tends 

 to remain more or less screened during the winter. Cases {a) and 

 (b) are now similar and new ice is added throughout the colder 

 months of the year, on the underside of the cover, where the water 

 is beyond the reach of severe atmospheric chilling. 



The fact that the amount of salt in sea ice varies directly with the 

 rate of freezing (inversely as the temperature), causes the top of a 

 glacon or Hoe. the part exposed to the coldest temperature, to be 

 composed of the saltiest ice.' Several writers on polar phenomena 

 have reported the presence of solid salt on the surface of ice sheets. 

 which sometimes coats them so heavily that it has been likened to 

 the early morning collection of hoar frost.*^ The growth in thickness 

 of young sea ice from the top surface downward proceeds at a 

 slower and slower rate the further the underside retreats from the 

 source of freezing. Similarly the insulating effect of a snow cover 

 in retarding the freezing processes is proved by the formation of 

 fresher ice on the underneath sides of those floes that are heavily 

 snow decked. The heat conductivity of ice is very poor, about one- 

 hundredth part that of iron. The upper surface of old ice being com- 

 l)aratively fresh is a much poorer heat conductor than is young, salty 

 ice. and similarly, retards freezing. A set of salinity observations by 

 ]\Ialmgren (19:28. p. 6) through the vertical cross section of a young 

 sheet, gives the following distril)uti()n of salt with depth : 



Deptli of ice from surface (em.) 6 13 25 45 82 95 



Salinity of the ice (0/00) 6.74 5.28 5.31 3.84 4.37 3.48 3.17 



The fact that the surface layers of the sea are normally fresher 

 than those deeper down ai)pears to have no appreciable effect in 

 varying the salinity of the ice, top to bottom, because its thickness 

 includes only a very snuiU part of the range of salinity witli (k^pth 

 of water. 



Since the undersiile of the cover is not only the freezing surface 

 l)Ut the plane of contact between the ice and the concentrated brine, 

 one might naturally reason that the thicker the ice became, the 

 I'icher it would groAV in salts. The fact that the salinity of ice 

 decreases with the de})th. liowever, indicates {<() that the processes 

 of pi'ecipitation are more than sufficient to counterbalance the increase 

 in salt concentration of the mother liquid; (b) that the mother 



"A thin veneer of new ice may often overlay young ice formed early in autumn from 

 the thaw water of the Arctic pack. 



" Weyprecht (1879, p. 58) states that the salt is not pure, but consists of fine needles 

 of ice tipped with small salt crystals. 



