SCIENTIFIC RESULTS 193 



in the winter chillino; of the surface hiyers in certain oceanic locali- 

 ties, notably from northeast of Jan Mayen to east of Cape Farewell 

 as shown by Wiist (1928, Tafel 35). / 



The heat of fusion exhibits itself in two forms, (a) when ice is 

 melted into water, as previously described, heat energy is consumed, 

 and (b) when water is frozen into ice heat energy is liberated. The 

 ice molecules represent a phase of less energy than the water mole- 

 cules, the difference l)etween the two phases being measured as heat 

 energy in terms of heat of fusion. If a gas be transformed to a 

 liquid or a liquid to a solid, heat energy is released and such heat 

 exchanges, for example, have been known to constitute one of the 

 main energizing components of cyclones. A rise in temperature 

 has also actually been observed at cloud altitudes when water vapor 

 has been rapidly precipitated into the rain of thunderstorms. In 

 the case of freezing, Avhen a quantity of homogeneous water mole- 

 cules are aligned into the compact uniform arrangement of ice crys- 

 tals, the heat energy released produces a material retardation in the 

 freezing processes -" and this phenomenon, moreover, is of such mag- 

 nitude in the polar regions that it tends to stabilize the seasonal 

 fluctuations. In other words, without the heat of fusion acting and 

 reacting, more ice would be formed in the colder months of the year, 

 and more and greater areas of open water would be found in summer 

 than is actually the case. 



Pettersson, in his laboratory experiment, has purposely stressed 

 the importance of the effect of ice melting rather than that of water 

 freezing, because in the first case the currents set up by the relatively 

 great immersion of the ice itself causes the cooling effect to spread 

 more comj^letely into the water itself than into the air. On the 

 other hand, when water in the sea is frozen as Pettersson points out, 

 the release of heat energy is not absorbed by the water but by the 

 atmosphere. It would be interesting to determine by tank experi- 

 ment what currents are really established in the water mass as a 

 result of freezing of the surface layers of salt water. It is difficult 

 to see why there should be any material difference over an extended 

 period in the disposition of heat in the case of these two ])rocesses — 

 radiation and absorption — regardless of the high specific heat of the 

 water, provided that the freezing and melting takes place in the 

 same general region. The recipients or contributors of the energy 

 are the surrounding media, i. e.. the atmosphere above and the sea on 

 all other sides. 



In order to obtain a clear insight into the extent to which the heat 

 of fusion may spread, it is necessary to take into consideration the 

 position and size of the areas of ice production and ice dissipation in 

 the North Atlantic and the physical state of the water which fills 

 the northern basins. The principal regions of ice formation and 

 dissipation agree well with the distribution of cold water. The ice 

 nucleus is centered in the heavy polar cap extending from which are 

 two arms one along the east coast of Greenland, the other along the 

 east coast of Arctic North America. This ice covers about one- 



■'■'' Barnes (1928. p. 2) describes the process of fusion as molecules of wattr are passing 

 from the liquid to molecules of ice in the solid state, each ice crystal Ijeing covered by a 

 heat mantle. 



