190 :\rAr.iox expeditiox to davis sti;ait axd baffix bay 



limits of the shelf waters is tlie reason for the areas of accumulation 

 and dissipation bein^- practically one and tlie same. The meltini:- area, » 

 it will be seen, includes not only the waters inshore of the continental 

 edjre, but a marginal mixing; zone. This strip naturally varies in 

 width depending to a great extent on the particular contour of the 

 slope, the direction of the current, and like factors at any given 

 locality. For example, off the Tail of the Grand Bank the belt of 

 mixed waters spreads out sometimes 60 to 100 miles or more in 

 width; a zone much broader than is found farther north in Lal)rador. 

 A conservative estimate of the average width of the mixed water 

 zone along the North American shelf is 30 miles. The greater 

 size of the melting area over that of the ice area is balanced, 

 however, by an area along the east coast of Baffin Land which 

 extends from Barrow Strait to Cumberland Gulf. Pack ice is 

 never absent from this region except for a week or two the first 

 })art of September, and tlien seldom more often than once in fom- 

 or five years. It is safe to designate this region as one in which no 

 melting prevails. The fact that it is in size just about equal to that 

 of the mixing zone causes ice area and melting area to be approxi- 

 luately equal, viz, 467.300 s(|uare miles. 



The estimate of 467.300 square miles of pack ice as the annual crop 

 is believed to be somewhat high, but it adds conservatism to our 1 

 figures on the magnitude of the ice-chilling effect to be introduced I 

 later. It should be also remarked that the pack ice area does not *" 

 jiresent a solid, unbroken surface, since leads and polynyas prevail 

 in the ])ack just the same, or to a greater degree, as they do in the 

 ])olar ocean. The figure of 10 per cent of open water for the polar 

 cap ice is believed to be also fairly representative for the pack ice 

 of Davis Strait and Baffin Bay. The 10 per cent value of open 

 water in the pack does not, however, materially effect, for |)urposes 

 of comparison, the roughly equivalent size of melting area and ice 

 area. 



In order to compare the annual amount of sea ice and glacial ice 

 in this interesting arm of the northwestern North Atlantic we have 

 assumed the average thickness of the pack ice to be 6 feet. Naturally 

 the floes and fields are thicker at the northern extremity of liaffin 

 Bay than they are much farther south near the melting end off 

 Newfoundland. Also Avhere rafting and hummocking has occurred f 

 the pack will be thicker than where young ice lies. But an average 

 of 6 feet is believed to be a fairly close approximation. The total 

 volume of sea ice melted annually is therefore 467 cubic miles. 

 Since over a long period of years there has been no tendency toward a 

 persistent increase or decrease in the geograjihical i)ositi()n of the ice 

 boundaries, it follows that during the course of a normal yeai- 467 

 cubic miles of water are frozen into ice and a like amount of ice is 

 melting into water.**- Compare this figure of 467 cubic miles of sea 

 ice Avith that of 7 to 10 cubic miles as the annual output of glacial 

 ice for Davis Strait and r)affin Bay. Though our figures nuiy only 

 be approximate, they unmistakably reveal, nevertiieless, that sea ice 

 aiiimalhj (/rcath/ e.cceedx (jlacidl ice in vohitne, the latter cqadliiig 

 only O.fll') to 0.02() of the foi i)>ei'. In fact evaporation of the inching 



*•- Specrsfhneidei- (1026, p 74) estimatfs an annual discharge fnniT the polar sea ofv«-i 

 2fi,0(i(».(Kio.(HMi fuhic yards. This is far tno small siiu-e. if n ft-et thick, it wctild :im(niiit 

 to an area iMiveiiiij; only 1° of longitudi' ami .■'.° of latiliidc off iioiilirasl < Irrcnlaiul. 



