when melting starts, the pack boundary in the area of the North Open 

 Water contracts and moves southward. Its western boundary facing Devon 

 and Bylot Islands recedes eastward. The Melville Bugt Pack begins to break 

 in the region of the Middle Passage, along a line connecting Upernavik 

 and Wolstenholme 0. Along the coast of Greenland a broad shore lead 

 forms, gradually moves northward into Melville Bugt joining the Northabout 

 Route, and the great pack recedes westward. The drift of the fragmented 

 pack gradually narrows to the south and withdraws toward Cape Dyer. By 

 the latter part of July the pack is rotted and reduced in size. The fast 

 ice of Baffin Island, already deteriorated, is leaving its coastal anchor- 

 age. In August the pack becomes a floating mass of rotten floes that 

 rapidly fall apart into brash and block. By mid-September the pack dis- 

 appears. 



During periods of optimum ice growth, passing storms greatly increase 

 the pressure on the Baffin Bay Pack. On such occassions large areas of 

 the pack are forced open forming leads. Some of the leads rapidly acquire 

 fresh layers of hard ice while others close and form pressure ridges along 

 lines of contact. The ice of the newly frozen leads is readily recognized 

 from its smooth surface and color. The color of the newly formed ice 

 depends greatly. on its thickness. It was observed that the thickness of 

 dark and gray ice ranged 6 to 8 inches, of lightest gray ice 8 to 14 inches, 

 and almost white 14 to 18 inches. In the extremely cold months of February, 

 March, and April, ice formed during periods of relatively light winds 

 takes on a glass-like surface. This ice may reach a thickness of 20 

 inches within a two-week period. 



Leads of the type described above are found in the northeast and cen- 

 tral part of the pack. They usually have a northwest-southeast orientation. 

 They frequently are irregular in size and may vary in width from a few 

 hundred feet to several hundred yards and attain a length of several 

 miles. Occasionally, they appear as a great network that may extend for 

 distances of 50 to 100 miles. 



The leads that form in the western part of this section of the pack 

 undergo rapid changes; hence, the newly formed ice usually is broken up 

 before a lead attains appreciable size. 



Under the influence of westerly winds, the northern sector of the 

 pack will separate from the Baffin Island fast ice, and a broad lead will 

 form from the vicinity of Home Bay to the latitude of Pond Inlet. Its 

 width depends on the duration and magnitude of the wind force exerted 

 against the pack. It may vary from a few miles to more than 20 miles. 

 Its life, however, is short and the pack soon crushes against the fast 

 ice and creates great ridges. 



Leads that form in the southern sector of the Baffin Bay Pack also 

 have a short life. The high mobility of the pack and the rapid changes 

 which occur as a result of different pressures, open and close leads 

 frequently. 



15 



