24 MARIOX EXPEDITION TO DAVIS STRAIT AND BAFFIN BAY 



ice line to climb as high as the spray clashes and to penetrate down 

 as far as the frigid temperature of the land is beloAv freezing. This 

 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 i)arallel to the shore and later in several. 



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

 of all sea-ice forms to melt. Beginning in the early part of spring 

 in the latitudes of Newfoundland, and sweeping northward with the 

 advancing sun, disintegration reaches along Arctic shores during 

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

 collecting in large pools and lagoons of " offshore water.'' The fast 

 ice ]datf()rm, 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 summer. The so-called famous Siberian Sea Road of the 

 Russians, has this origin. 



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

 upon the rate of ])roduction of icebergs, and also upon their subse- 

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

 efl'ect runs all the way from entirely preventing production to 

 blocking, tem})orarily, 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." whicli effectually prevents the glaciers from ever 

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

 P^skiuio. uieaning " very old ice." and was first used by Rasnuissen 

 (11>15. ]). ;)5s) for sea ice which after two to five years has gradually 

 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 Greenland type. It is at least 2.") years old, 

 therefore the oldest fast ice known. 



Fast ice which has not ac<{uired the age of sikussak may lie in 

 front of glaciers, })enning uj) the icebergs for an indefinite period. 

 (See fig. 39, p. 80.) The Great Hunfljoldt Glacier in northwest 

 Greenland experiences such a blockade which may last 20 to 30 years, 

 or which may be f)r(>ken by an especially favorable sunnner when the 

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

 drift southward. Some of the rich iceberg years in the North 

 Atlantic may reflect some of these events. 



Along other coast lines and in other ice fjords fast ice may blanket 

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

 West Greenland. ])articularly those in Disko and Northeast Bays 

 that supi)ly so much of the North Atlantic quota, are normally cov- 

 ered by fast ice only during the colder months, from November to 

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

 ter's collection of bergs is released to float out into Disko Bay. 

 Fast ice, therefore, causes a seasonal pulse in the presence of ice- 

 bergs in Davis Strait where otherwise the regular flow from the ice 

 cap itself would cause a more or less steady distribution the 3'ear 

 roujid. 



