DISCUSSION OF SOME OF THE EFFECTS OF WINDS 



ON ICE DISTRIBUTION IN THE VICINITY OF THE 



GRAND BANKS AND THE LABRADOR SHELF 



BY FLOYD M. SOULE AND E. R. CHALLENDER' 



The movement of a floating object, such as a piece of ice, is con- 

 trolled by the movements of the water surrounding the submerged 

 portion of the object and the air surrounding the portion of the 

 object which extends above the water line. The relative importance 

 of winds and currents in contributing to the motion of the ice de- 

 pends in large measure upon the shape of the piece of ice and the 

 consequent proportion of the surface areas exposed to the two 

 media. Thus the movement of a berg is usually controlled almost 

 entirely by currents, whereas the movement of a field of sea ice is 

 more affected by winds than by currents. Neither type of ice will 

 be completely independent of either winds or currents. An estab- 

 lished current system is the result of all of the factors which have 

 been operating to produce forces tending to move or direct the 

 motion of the water during a period of time in the immediate past. 

 Probably the most important of these factors is the wind. The 

 length of the period of time, immediately past, which needs to be 

 considered as making significant wind-originated contributions to 

 a current system is obscure. Winds prevailing for as much as a 

 month have a pronounced effect on a current system. Winds asso- 

 ciated with an individual storm lasting for about 2 days set up wind 

 currents whose effects disappear with the passage of the storm. The 

 effect of wind on floating ice is brought about by the direct action 

 of the wind on the exposed part of the ice and by the indirect action 

 of the wind on the submerged part of the ice through the alteration 

 of the currents. The time factor becomes of greater importance 

 when the draft of the ice is in the order of magnitude of 100 to 300 

 meters as it is in the case of bergs. 



Because so little is known about the effect of wind on the drift of 

 ice there are recorded here some data pertinent to the meteorological 

 conditions which accompanied the unusual ice distribution observed 

 during the 1947 season. Seemingly normal or abnormal amounts of 

 both sea ice and bergs were in prospect for the 1947 season. The 

 forecast, made by the use of the Smith- formulae, was for 550 bergs 

 to drift south of latitude 48° N., compared with the 48-year average 

 of 431 bergs. During the month of February the barometric pres- 

 sure distribution was abnormal and along the Newfoundland- 

 Labrador coast an unusually large proportion of onshore winds 

 resulted. During February all of the field ice was destroyed and 



^ Contribution No. 463 of the Woods Hole Oceanographic Institution. 



2 Edward H. Smith, The Marion Expedition to Davis Strait and Baffin Bay, U. S. Coast Guard 

 Bull. 19, part 3, 188 (1931). Washington. 



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