24 MARION EXPEDITIOX TO DAVIS STRAIT AND BAFFIN BAY 



ice line to climb as high as the spray dashes and to i)enetrate down 

 as far as the frigid temperature of tlie land is below freezing. Tliis 

 thickening of the sheet combined with the rise and fall of its seaward 

 side, causes it to fracture first in one tidal crack running adjacent 

 and parallel to the shore and later in several. 



Fast ice not only '' makes " first in autumn but it also is the earliest 

 of all sea-ice forms to melt. Beginning in the early part of si)ring 

 in the latitudes of Newfoundland, and sweeping northward with the 

 advancing sun. disintegration reaches along Arctic shores during 

 ]\Iay. The land snow, in melting, flows out on top of the fast ice 

 collecting in large i)ools and lagoons of '" offshore water." The fast 

 ice platform, for a few weeks, holds tightly until the heat from the 

 sun penetrating downward opens up the floes, and allows these pools 

 to drain away. Then sand and detritus from the land now bare, 

 honeycomb the ice. Soon the sheet gains a slight movement along 

 the coast, uncovering a lane of open water which persists there for 

 the entire smnmer. The so-called famous Siberian Sea Road of the 

 Russians, has this origin. 



Fast ice is of particular importance as it exerts a direct inflnencT 

 upon the rate of production of icebergs, and also upon their subse- 

 (pient movement once they have calved from the glaciers. The 

 effect runs all the way from entirely preventing production to 

 blocking, temporarily, the passage of the bergs toward the open 

 sea. Several fjords in northern (Ireenland, Frederick Hyde, and 

 Bessels, for example, are covered between the glacier front and the 

 fjord entrance by a very old, heavy ice which Koch (1926. p. 100) 

 calls " sikussak."' which effectually prevents the glaciers from ever 

 discharging any bergs into the fjord. The word " sikussak " is 

 Eskimo, meaning " very old ice," and was first used by Rasmusseii 

 (1915, p. 358) for sea ice which after two to five years has graihiallv 

 become fresh throughout, and roughly granular in structure, so that 

 it is indistinguishable from glacier ice. Sikussak has a very limited 

 geographical distribution and is found only in calm, undisturbed 

 fjords of the north (ireenland type. It is at least 25 years old. 

 therefore the oldest fast ice known. 



Fast ice which has not acfpiired the age of sikussak may lie in 

 front of glaciers, penning uj) the icebergs for an indefinite j)enod. 

 (See fig. 89, p. 80.) The (ireat Humbohh (ilacier in northwest 

 Greenland experiences such a blockade Avhich may last 20 to 8<> years, 

 or Avhich may be broken by an especially favorable summer when the 

 accumulation of hundreds, possibly thousands, of bergs is freed to 

 drift southward. Some of the rich iceberg 3^ears in the Xorth 

 Atlantic may reflect some of these events. 



Along other coast lines and in other ice fjords fast ice may bhu^.ket 

 the bergs for only a part of the year. Tims the iceberg fjords of 

 AVest (ireeidand. particuhtrly those in Disko and Xoitheast Bays 

 that supi)ly so nuudi of tlie North Atlantic (juota. are normally cov- 

 ered b}' fast ice only during the colder months, fi'om November to 

 June. When the ice breaks away, usually in May or dune, the win- 

 ter's collecti(m of bergs is released to float out into Disko Bay- 

 Fast ice, therefore, causes a seasonal ])ulse in the presence <>f ice- 

 bei'gs in Davis Strait where otherwise the regular Mow from the ice 

 i-ap itself would cause a more or less .steady distribution the year 

 roujid. 



