RESTRICTED 



Under the influence of variable winds the ice, in all seasons of the 

 3'ear, is torn apart in some localities forming lanes of open water, 

 and elsewhere is crowded together. "Wliere lanes are formed the ice 

 always breaks along a jagged line, and when the ice fields move apart 

 they may also be displaced laterally. In summer such lanes do not 

 re-freeze. When they close due to change in wind direction, the two 

 sides of the lane do not fit : corners meet corners and openings of dif- 

 ferent shapes remain between the corners. "Arctic sea smoke"' may 

 sometimes be noticed wherever cracks in the ice appear, particularly 

 in areas where there is considerable open water. 



The belts of pack ice usually lie perpendicular to the prevailing 

 wind. Tongues may be formed in the belt by a wind blowing nearly 

 parallel to the axis of the belt, resulting in a bend of the ice edge. 

 In regions where currents augment the influence of the parallel wind, 

 a vast bend may occur redefining the limit of the f)ack. 



Bays or bights may be formed by wind in a belt of pack ice ; the 

 degree of openness and the physical character of the ice forming the 

 belt greatly determine the resistance offered b}^ the ice. Wliere wind 

 produces this effect the embayment is usually small. Bays may also 

 be formed in the pack under the influence of currents, sometimes of 

 huge dimensions. 



Often consolidated pack, the heaviest form of pack ice, will drift 

 from shore or will separate, forming leads or passages through the 

 ice area. Massive detachments of ice resulting from hummocking are 

 called floebergs. These should not be confused with icebergs, or 

 growlers, which are of glacial origin. Pressure ridges are formed by 

 a very large external loose floe riding upon a fixed floe or upon the 



Figure 8. — Tidal currents acting on grounded ice produce the mushroom-looking pieces of ice, 

 whose shape is visible at low tide. 



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