194 MAltlOX EXPEDITIOX TO DAVIS STRAIT AND BAFFIX BAT 



fourtli of the total surface of tiie Xoitli Atlantic. Arctic Ocean in- 

 cluded, of which ab!)ut one-sixth is nonnally frozen and melted each 

 year, so tliat one-thirtieth of the entii'e surface of the Atlantic is 

 annually exposed to the latent heat ])lienoniena. A comparison of 

 vertical dimensions shows that only about 0.001 of the mean depth 

 of the Atlantic is ice filled and if volinnes are matched, only 0.0005 

 of the entire ocean is <j:iven over to ice. It is obvious from this tiiat 

 the proportions, horizontal to veitical. definitely prove the ice proc- 

 esses as wholly superficial. 



The principal reofions of ice i)roduction are the coastal seas of 

 Pvurasia and the oflin<r of the latter, of east Greenland, and of 

 Arctic Xorth America. The ])rincipal rejjfions of ice ])ro(hiction are 

 also the oeneral retjfions in which the ice melts in greatest amount 

 (hii'in<i: summer. It follows that the life cycle of nearly all the ice 

 is s])ent in waters whose outer bounds are the continental edfres, and, 

 althoufjh a certain quantity of ice is carried out into the deep 

 ocean basin, this forms only an exceedino'ly small ])roportion of 

 the wliole. 



Tlierefore, the raw materials, so to sj)eak. out of which the irreat 

 mass of ice is created, and back to which it returns, are the irreat 

 reservoirs of shallow coastal waters of the north. Durino- the colder 

 months of the year, dependin<r ui)on the severity of the air tempera- 

 tures, these become readily chilled (from the top down to dei)ths 

 of 100 to 200 meters) close to the freezing point and ice forms in 

 large amounts on the surface. Thus the actual appearance of the 

 ice marks the release of heat energy, partly to the atmosphere and 

 partly to the water, but the creation of the surface covering of ice 

 tends to insulate the dee])er waters and thereby protects them from 

 further ra])i(l freezing. The low temperature of the atmosj^here, 

 therefore, i)roduces over shelves and northern seas, at the end of 

 winter, a relatively deep frigid body of w^ater, in the upper few 

 feet of which then floats a covering of ice. It is obvious that prac- 

 tically no melting, hence no withdrawal of heat energy from the 

 water, can take |)lace even on the underside of the ice, as some have 

 claimed, while it lies insulated in such boreal surroundings. 



Witii the api)roach of summer increased radiation from the more 

 ])er])en(Hcular rays of the sun becomes a])|)lied to (a) the top of 

 the ice cover, and (h) to the surface water where this is exposed. 

 The ice and water are thus warmed sinudtaneously, but due to the 

 far greater capacity of the water to absorb heat and also to spread 

 the heat rapidly downward to 10 to 25 meters, the ice is soon com- 

 pletely enveloped, even on its underside, by relatively warm water. 

 The sun-warmed surface layers, moreover, due to their great specific 

 heat, are uuich more effective as a melting agency than are the 

 direct rays of the sun on the ice itself. The latent heat of melting, 

 it is true, tends to retard the ablation of the ice but continued solar 

 radiation striking its suid'ace more than counterbalances this. As the 

 ice melts it loses draft and, floating higher and higher, it becomes 

 more and more confined to the sliallowest and warmest stratum 

 which materially accelerates the rate of its dissipation. All this is 

 made evident l)y the shrinkage of the floes, by the expansion of tlie 

 areas of oix-n water between the fields, and by the growth of char- 



