SCIENTIFIC ItESULTS 17 



Lead or lane. — A navigable passage througli any kind of pack ice. 



Pressure ridge. — The marginal elevation and heaping up of any 

 kind of pack ice when opposing forces press it together. 



Pohjnya {Russian). — Any sizeable water area, not a crack or a lead, 

 which is surrounded by sea ice. 



Pool. — A depression in the fields, floes, or gla(,'ons that contains 

 fresh water. 



Frost smoke. — The foglike clouds that form over newly opened 

 water areas in sea ice in the far north. 



^yater shy. — Dark streaks on the clouds due to the reflection of 

 polynyas, or of the open sea, in the vicinity of large areas of ice. 



Ice hUnk. — The whitish hazy glare on the clouds or near the 

 horizon produced by the reflection from large areas of sea ice in the 

 vicinity. 



Iceberg. — A large mass of glacier ice found in the sea. 



Growler.— 'X low-lying piece of glacier ice not so large as a berg. 



Classification of Sea Ice 



The ice cover that spreads over northern seas, for clearness and 

 simplicity, may be classified in accordance with its distribution, i. e., 

 in the form of concentric belts, focused around a center called the 

 ice pole, normally located in the vicinity of latitude 83° to 85°, 

 longitude 170° to 180° west. The southernmost boundary of the 

 outer circunii)()lar region coincides with the southernmost sea area 

 which becomes ice covered, either because of freezing temperature or 

 through drift of the ice from colder regions. The southern limit 

 of sea ice naturally deviates from the latitude parallels because of 

 many varied conditions, such as the distribution of land and sea 

 masses, the bathymetrical features of the ocean basins, the ocean 

 currents, and the winds. All these factors tend to modify a sym- 

 metrical arrajigement which otherwise would designate the geo- 

 graphical pole as the iciest spot on the earth. 



The ice cover of northern waters may be classified as follows : 

 {a) Fast ice; {h) north polar cap ice; (c) pack ice. 



Fast ice (Transehe 1928. p. 99), or winter ice (Koch 1926, p. 101), 

 refers to the sheet that forms in coastal zones during winter, and that 

 is rendered immobile by attachment through the ice foot to the shore. 

 Xoi'th polar cap ice is the ice which throughout the year covers 

 the deep central, major portions, of the north polar basin. It is 

 chiefly distinguished by great solidity; by the great size of its fields; 

 and by the massiveness of its rafted hummocks. Pack ice consists 

 mostly of fast ice that has broken away, supplemented in certain 

 regions by minor additions from the polar cap ice. It is found 

 aiound the outer borders of the Arctic Ocean; dominates its marginal 

 seas, the sounds of the American Archipelago. Baffin Bay. Davis 

 Strait, and the waters of east Greenland. 



The annual cycle which witnesses the formation or depletion, as 

 the case may l)e. in the varying areas occupied by the three types — 

 fast, polar cap. and pack — displays the following features. AVe start 

 with the formation of fast ice in winter, as Avell as the solidification 

 of and accretion to both the already existing pack ice and the polar 

 cap. The approach of sjjiiiig and summei' causes the fast ice to 



