SCIENTIFIC EESULTS 21 



of the north into lower latitudes, or {e), it melts and disintegrates 

 during summer near, or at, its source. Polar cap ice comes under 

 the intiuence of powerful conflicting forces which causes it sometimes 

 to persist for four or five years, and possibly longer, before leaving 

 the polar basin. 



Three Forms of Sea Ice 



FAST ICE 



The ice cover of northern seas thousands of years ago probably 

 had its genesis in fast ice fringing polar shores. Once the nucleus of 

 the permanent cap was built from the dismemberment and offshore 

 scattering of the fast-ice belt — and survived the first fcAv summers — 

 the latter lost much of its geographical importance. The wide dis- 

 tribution of fast ice in coastal waters, however, serves to make it 

 representative for such zones. 



The initial appearance of slush and sludge takes place in water 

 lanes of the Arctic early in September, first in the sounds of the 

 American Archipelago, then in the marginal Arctic seas, and in 

 Baffin Bay in swift succession. Small pancakes soon cement, rim 

 to rim, in a continuous sheet of young ice and preparations are made 

 by man and beast to meet the rapidly approaching grip of winter. 

 Hudson Bay and Fox Channel in the American sector see their first 

 fast ice during October, with freezing spreading to Newfoundland 

 and to the Gulf of St. Lawrence late that same month, or early in 

 November. 



Fast ice continues to " make " until it reaches a maximum area in 

 December after Avhich, until May. it builds very little farther out 

 from the coast, but continues steadily to increase in thickness. 



The regions of growth for fast ice largeh- reflect bathymetrical 

 conditions. Other important influences are the degree and duration 

 of low air temperatures; the decrease of salinity due to snow melting; 

 to river discharge and to precipitation; the amount of storminess; 

 and the presence of grounded hummocks, icebergs, and floes of 

 pack ice. 



The seats of fast ice are the broad continental shelves and the 

 flat spacious embayments. The most striking example of such a 

 region is the remarkably wide Siberian shelf which has a mean width 

 of 400 miles and a depth of 12 to 50 fathoms, its outer edge forming 

 a " steep " slope facing the polar ocean. ^^ These regions jjroduce 

 a vast amount of fast ice (see fig. 11, p. 20) because («) the shallow 

 depths favor early chilling, and (6), the sea freezes more rapidly 

 where it has been diluted by Siberian rivers.^* It is estimated that 

 approximately 150.000 square miles of fast ice form every winter 

 from Wrangel Island to Northern (Nicholas II) Land. It has an 

 avei-age tliickness of Gi/4 feet, ranging all the way from to 9 feet. 



Anotlier large area of fast ice, second only to Siberia, is the sheet 

 covering the hdn'rinthlike waterways of the American Arctic Archi- 

 ll Transehe (1928. p. 102 » states that fast ice extends about 275 miles out from the 

 coast opposite the Yana River, longitude 135° E. 



" Wiese (1922, p. 271) calls the Siberian shelf and the fringing Arctic seas "The fac- 

 tory of northern polar ice."' According to his theory the air temperatures along the 

 Siberian coast are an index of the size of the Greenland Sea pack 4i^ years later. This 

 Interval represents approximately the time required for a piece of ice to drift from Arctic 

 shores to the Greenland Sea, aiid a high correlation of 0.83 appears to support such a 

 contention. 



