The freezing point drops with an increase in pressure, i.e. , the ice which had formed melts 

 with increased pressure. This in particular explains the fusion of ice floes due to compression. 



Theoretically, the freezing point drops 1° with a pressure increase of 134.4 bars. 



The temperature of maximum water density, according to Amaga, drops 1° with a pressure 

 increase of 40.5 bars. At a pressure of 146.6 bars, it is 0.6°. 



It should be noted that any ice , and in particular sea ice , is permeated with capillaries . The 

 freezing point decreases in the capillaries, e.g. , Lange showed that a temperature of -18° is re- 

 quired to cause fresh water to freeze in a capillary . 1 mm in diameter . 



LITERATURE: 62, 73, 97, 154. 



Section 6. Increase in Density During Mixing 



Since the temperatures of freezing and of maximum density do not coincide, near the temper- 

 ature of maximum density for briny waters, a region of temperatures forms in which water of the 

 same salinity may have the same density at two different temperatures. Thus, e.g. , the density of 

 distilled water is the same at 0° and at 8.2°. Curve fl- in figure 2 is a curve of temperatures lying 

 above the temperature of maximum density, but at which the density of the water is equal to the 

 density of water of the same salinity at the freezing point. This property of water is responsible 

 for the " increase in density with mixing. " 



Let us mix two equal parts of fresh water: one with a temperature of 8.2°, the other 0°. The 

 density is 0.99987 in each case. After mixing, the temperature of the mixture will be 4.1°, the 

 density about 1.00000, i.e. , 0.00013 greater than that of each of the mixed parts taken separately. 

 Densification during mixing of waters of the same salinity is possible for sea water with a salinity 

 of less than 24.695 o/oo, between the freezing temperature and the temperature which can be deter- 

 mined by the ^ curve of figure 2. But further, as can be seen from the TS diagram, for sea waters 

 of any salinity and temperature but of the same density, the density after mixing is always greater 

 than the density computed from the mixing formulas, particularly at low temperatures and salinities. 

 This phenomenon is fully explained by the convexity of the curves of equal density. 



Table 2 shows the temperatures and salinities of waters of equal density and their tempera- 

 tures, salinities and natural densities after equal masses of the examined waters have been mixed. 

 As can be seen from the table, when equal masses of water are mixed, one of which has a tempera- 

 ture of -1.6° and a salinity of 27.38 o/oo (approximately corresponding to the waters of the 

 Labrador Current) while the other has a temperature of 30.0° and salinity 35.36 o/oo (approximate- 

 ly corresponding to the waters of the Gulf Stream), and with a natural density of 22.0 for both wa- 

 ters before mixing, we find a common temperature of 14.2°, salinity 31.37 o/oo and natural density 

 23.39. Thus, in the case examined, the natural density increases 1.39 due to mixing, which is 

 quite an appreciable amount. Actually, a similar effect is obtained for water No. 2, either by in- 

 creasing the salinity 1.82 o/oo or by decreasing the temperature 4.2°. 



The magnitude of density increase during mixing and the mixing proportion causing maximum 

 density increase can be determined most simply from the TS diagram. On the TS diagram, let us 

 join the two TS points characterizing the mixing waters by a straight line. Let us call this line the 

 "mixing line" . Actually, with any mixing proportion, the TS point of mixture lies on this line. If 

 we compare the densities taken from the TS diagram with those computed from the mixing formulas, 

 we will get the magnitudes of density increase . Under certain conditions the density of the mixture 



14 



