105 



The actual range of density of glacial ice in the Grand Banks region 

 should be checked by more observations. 



The size of the average berg has been taken great enough to insure 

 that no large underestimation can be introduced into the final figures by 

 the slight uncertainty that still exists relative to the average specific 

 gravity of the ice. Therefore, multiplying the average berg's 4 

 million cubic feet of above water ice by five, we find that on entering 

 the waters about the Grand Banks it contains not over 20 million 

 cubic feet of ice in all, or, in other words, has a total mass slightly in 

 excess of 500,000 short tons. 



The total amount of berg ice, both above and below water, south of 

 the forty-eighth parallel in 1929, may, therefore, be estimated as 

 thirteen hundred times 20 million or 26 billion cubic feet, which is 

 roughly about 676 million short tons. Such an amount of ice would 

 require well over 100 trillion British thermal units to reduce it to water 

 at 32° F. This is a formidable amount of heat, for each British 

 thermal unit is equal to 252 gram calories. 



It is with this draft of heat that icebergs melting south of the forty- 

 eighth parallel directly affect the temperature of the waters in which 

 they are distributed. As soon as the area in which the 26 billion 

 cubic feet of ice melts is estimated, the possible eft'ects on water layers 

 in the area can be computed. 



The isotherm and ice maps show that the cold waters that would be 

 directly aft'ected by this melting ice extend over about 20,000 square 

 sea miles south of the Tail, 30,000 square sea miles along the eastern 

 e6.-7,e of the Banks, and 24,000 square sea miles between the forty- 

 seventh and forty-eighth parallels. (See figure 1.) This is a total 

 area of 74,000 square sea miles or 2,644 billion square feet. 



Hereafter this area will be referred to as the "melting area." The 

 section of it to the south of the Tail, and the southern half of the sec- 

 tion of it along the eastern edge of the Banks, include the whole of 

 the 13,200 square sea-mile critical triangle of the patrol described in 

 the chapter on procedure and remarks. They include the waters that 

 surround the critical triangle as well. The northern parts of the 

 "melting area" include all waters through which the bergs pass to 

 reach the critical triangle. 



It was also stated in the discssion of the practical problems of the 

 patrol that berg ice is normally found each year inside a 150,000 

 square sea-mile area south of the forty-eighth parallel. The "melting- 

 area" is the very heart of this usual ice area, and inside of it fully 

 90 per cent of the ice that comes south of the forty-eighth parallel 

 can be expected to melt. To draw comparisons so that the size of 

 the "melting area" can be more readily visuahzed, its 74,000 square 

 sea-mile extent is a little larger than the six States that comprise 

 100277—30 8 



