112 



a long period of fog shuts down are invariably lost. After a protracted 

 foggy spell the patrol does its most intensive cruising, trying to 

 relocate the new positions of the dangerous bergs. 



Each year a certain amount of time is lost in futile searching for 

 bergs reported from extra southerly locations. These bergs frequently 

 can not be found because of the strong currents and rapid ice dis- 

 integration, which obtain in the warm surface waters along the northern 

 edge of the Gulf Stream. 



Besides the rather limited opportunities for close first-hand observa- 

 tion, the varying shapes of the bergs themselves, and the varying 

 conditions of wave motion and water temperature about them, all 

 go to make the subject of berg disintegration a complicated and con- 

 jectural one. The determination of the life of a berg that is sighted 

 south of the Tail of the Banks is certainly not obtainable through the 

 application of any hard and fast rules. 



Obviously 130,000 tons of ice in the form of growlers and small 

 pieces will melt much faster than the same amount of ice in the form of 

 a single solid berg. Not only will the smaller pieces have a greater 

 total area exposed to water action, but they will be entirely in the 

 upper layers of water that are warmer and more affected by wave 

 motion than the layers that are 50 feet and more below the surface. 

 The pieces of ice that calve from a berg nearly always stream off to 

 leeward, under the influence of winds, waves, and surface currents. 

 They rapidly melt and disappear and the life of the parent berg is 

 undoubtedly materially shortened by continued prolific calving. 

 Some of the bergs, because of their peculiar shape and particular 

 internal structure, or the unusual conditions of water and weather 

 that they experience, calve more than others. 



The fresh ice exposed when a piece falls from a berg south of the 

 forty -fourth parallel is dry and frosty at first. The spot, even though 

 far above the reach of sea and spray, soon becomes wet, however, and 

 so it generally remains. After long exposure the upper parts of bergs 

 sometimes become rough and granular and apparently dry, while 

 between the granules they may be wet in fact. 



Barnes ^ states that bergs calve most near sunrise and that they dry 

 up and freeze on account of radiation from their surfaces at night. 

 This may be true of bergs north of the Grand Banks, but that it is 

 true of bergs melting in the warmer southern portions of the "melting 

 area" south of the forty-fourth parallel should not be assumed with- 

 out more direct evidence. On the contrary, the late afternoons, 

 nights, and early mornings are foggy or cloudy more than 50 per cent 

 of the time during the ice season in the southern parts of the "melting 

 area." Such conditions are not conducive to eft'ective nocturnal 

 chilling of berg surfaces by radiation and keep as well the early rays 



* H. T. Barnes, " Thermit and Icebergs." Journal of the Franklin Institute, May, 1927. 



