TABLE 45. THE DENSITY OF PURE ICE 6ot SUPERCOOLED WATER 6^, 



AND SALT-CELL BRINE 607. AT DIFFERENT TEMPERATURES 



When examining table 46, we see that the density of sea ice which has no air bubbles in con- 

 nection with a change in its temperature and salinity changes comparatively little, but it discloses 

 a characteristic property, namely, when the temperature of sea ice changes, its density crosses 

 the minimum. This phenomenon is completely within the law. 



TABLE 46. THE DENSITY OF SEA ICE AT DIFFERENT TEMPERATURES 

 AND SALINITIES AND WITHOUT AIR BUBBLES 



-6 



0.920 

 0.924 

 0.926 

 0.929 

 0.931 

 0.939 



0.921 

 0.923 

 0.926 

 0.928 

 0.929 

 0.937 



-10 



0.921 

 0.923 

 0.926 

 0.928 

 0.929 

 0.935 



-15 



0.922 

 0.923 

 0.925 

 0.928 

 0.929 

 0.934 



-20 



0.923 

 0.925 

 0.926 

 0.929 

 0.930 

 0.935 



-23 



0.923 

 0.925 

 0.926 

 0.929 

 0.930 

 0.935 



Actually we have seen in Section 63 that the coefficient of the volumetric expansion of 1 g of 

 sea ice, according to Malmgren, is determined by the approximate formula 



u, =0.000169 — 0.091 



5i_ dS^ 



(6) 



The first number on the right side of this equation, according to Malmgren, is the coefficient 

 of the thermal expansion of 1 g of pure ice. The second is the correction for salinity which char- 

 acterizes the change in volume as a result of the formation or melting of a certain amount of pure 

 ice in the brine cells during the change of temperature. 



In formula (6), the fundamental difference between sea ice and fresh ice becomes apparent. 

 The density of fresh ice increases with a decrease of temperature. The density of sea ice, when 

 it has low salinity and a low temperature, also increases with a decrease in temperature, although 

 to a lesser extent than the density of pure ice. But at high salinities and comparatively high tem- 

 peratures, the density of sea ice decreases with the decrease in temperature. Therefore, the 

 concept introduced by me for minimum density of sea ice as a function of temperature and salinity 

 is based upon this. I have made use of Malmgren' s formula (6) for the corresponding computations. 



164 



