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to gather together and move along, retaining the openings between. 

 Heavy onshore winds and swell break up the ice, and if offshore winds 

 follow, the ice will open out, making the waters navigable. Once 

 broken up in mild weather, the pack ice will not recement if brought 

 together again, and consequently will open more readily to light winds. 



Proceed through the lanes thus formed, even if they do not lead in 

 exactly the same direction as the vessel's course; by proceeding 

 through weak patches in the ice from one lane to another, a ship can 

 thus make good her course. To avoid ultimately taking the vessel far 

 from its objective, it should be impressed upon conning officers that 

 the compass must be closely watched while navigating leads and care 

 taken to adhere within reasonable limits to the base course. 



An offshore wind usually forms a channel between the coast and 

 the pack ice which is frequently used by navigators, who must, how- 

 ever, be on guard against an onshore wind setting the ice back onto the 

 coast. In such a case, shelter should be sought in a bay, behind an 

 island, or even behind a floe. The alternative is to proceed out to meet 

 the ice so as to work a way through it to clear water beyond, before 

 the floes pile up on each other against the land. However, this can 

 only be done where one is reasonably sure of finding open water well 

 away from the coast ; it must never be done on coasts like the north 

 shore of Alaska, unless direct information of open water offshore has 

 been received. Northward of western Canada, Alaska, and Siberia, 

 the amount of ice to be met increases with the distance from shore. 



Bergs in the pack should be given a wide berth as they are usually 

 current-driven, while the pack is wind-driven. Owing to their depth 

 below the surface, bergs travel with the current and are only slightly 

 affected by the wind. In pack, bergs generally move at a different 

 rate from the sea ice. In regions of strong currents they may travel 

 up-wind, wrecking heavy pack in the way and endangering a vessel 

 unable to work clear. Under these conditions open water will be 

 found to leeward and piled-up pressure to windward of bergs. The 

 same condition has been observed in regions where currents are weak. 

 In a strong wind, the pack overtook the bergs and was heaped up 

 to windward, while a lane of open water lay to leeward of the bergs. 

 This condition produced the optical illusion that the bergs themselves 

 were traveling in a direction opposite to the pack. 



If it becomes necessary to lie-to in a polynya, it is not always desir- 

 able to choose the vicinity of icebergs since they do not move with 

 the pack ; the opening is therefore apt to close up. Furthermore, there 

 are usually gi-owlers in the vicinity of bergs. There is danger in 

 making fast to bergs in bad weather, for they are often in motion and 



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