SCIENTIFIC ItESULTS 17 



Lead or lane. — A navigable passage throiigli 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. 



Polynya {Russian) . — Any sizeable Avater area, not a crack or a lead, 

 which is surrounded by sea ice. 



Pool. — A depression in the fields, tloes, or gla(,^ons that contains 

 fresh water. 



Frost s^moke. — The foglike clouds that form over newly opened 

 water areas in sea ice in the far north. 



Water sky. — 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 hi ink. — The whitish hazy glare on the clouds or near the 

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

 ivicinity. 



1 Iceherg.- — A large mass of glacier ice found in the sea. 

 I Growler. — A 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 circumpolar 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 

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

 biasses, the bathymetrical features of the ocean basins, the ocean 

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

 metrical arrangement 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 b}- attachment through the ice foot to the shore. 

 jNorth polar cap ice is the ice which throughout the year covers 

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

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

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

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

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

 iaround 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 be, in the varying areas occupied by the three types — 

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

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

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

 |cap. The approach of spring and summer causes the fast ice to 



