I20 POLAR PROBLEMS 



approximately along the 84th parallel; (3) the southward discharge 

 through Robeson Channel of part of the ice of Lincoln Sea (the 

 enlargement of the Arctic Sea bounded by the coasts of Grant Land 

 and northern Greenland) ; (4) a westward surface current along the 

 northern shores of Greenland (observed by Lauge Koch). 



Analyzing these facts and data we may come to the following 

 conclusions : 



The fact itself of the shock and pressure of the Arctic Pack upon 

 the shores points to the difference between the causes respectively 

 producing the Big Lead and the Great Siberian Polynya. In the case 

 of the latter, the main cause governing the formation of the polynya 

 is the general direction of the Arctic Pack motion away from shore. 

 Hence the Big Lead can develop no such width as that of the Great 

 Siberian Polynya. 



The fact itself of the shock and pressure of ice masses upon these 

 shores is due to the circumstance that, from the meridian of 90° W. 

 to Cape Bridgman (26° W.), the Arctic Pack probably maintains a 

 constant drift to the east (with a slight tendency to the southeast). 

 This very direction, in connection with the trend and position of the 

 shores of Grant Land and northern Greenland, must produce this 

 shock and pressure of ice masses on these shores (its maximum should 

 be at Cape Bridgman). 



The resistance of these shores to the motion of the Arctic Pack, 

 which, as a body, rushes towards its outlet into Greenland Sea, brings 

 it about that Lincoln Sea (which represents a bay, as it were, in rela- 

 tion to this motion of the Arctic Pack) is filled up with ice masses 

 derived from the Arctic Pack about up to the parallel of 84° N. 

 But as the main body of the Arctic Pack seeks an outlet into Greenland 

 Sea, its outskirts slide along this parallel, so to speak, toward the 

 east and make a line of demarcation between the main body of the 

 Arctic Pack, which is drifting to the east to its outlet into Greenland 

 Sea, and those parts of its outskirts with which Lincoln Sea has been 

 filled and which press on the shores under the pressure of the Arctic 

 Pack itself. 



This line of demarcation consequently is a place of possible forma- 

 tion of the Big Lead under the influence of sufficiently strong winds 

 and favorable tidal currents. 



Owing to this sliding of the Arctic Pack along the parallel of 

 84° N., its outskirts feed Lincoln Sea with that many-years-old, 

 hummocked, piled-up, and broken ice (the " paleocrystic ice")^® 

 that, under the influence of this pressure upon the shore, is partly 

 carried out to the south through Robeson Channel. 



. w This, in agreement with Lauge Koch (Ice Cap and Sea Ice in North Greenland, Geogr. Rev., 

 Vol. 16, 1926, pp. 98-107; references pp. 101-104), and not the iceberg derivation theory of the ex- 

 plorers of the seventies and eighties of the last century, whose deductions were necessarily based on 

 a more limited body of observations than is available today, seems the plausible explanation of the 

 origin of the so-called "paleocrystic ice." 



