to obtain precise positions, some investigators 

 placed marker buoys in shallow water and plotted 

 positions relative to the buoy. This procedure 

 had at least two drawbacks. The first was that 

 the berg could only be tracked for a limited dis- 

 tance before the marker had to be moved. Second, 

 using a buoy required that the drift study be 

 conducted in shallow water where tidal currents 

 and turbulence had a much greater impact than 

 in the deeper ocean. 



Now that satellite navigation is available, it is 

 possible to plan a more precise and more sophis- 

 ticated approach to iceberg drift. 



The elements that contribute to the dirft of an 

 iceberg are as follows : 



a. The current system, composed of barotrophic 

 and baroclinic components, is probably the most 

 influential factor in iceberg drift. 



b. The wind has two effects on iceberg drift. 

 First, the drag on the iceberg itself by the wind. 

 Second, the wind-included current which adds to 

 and modifies whatever surface current already 

 exists. 



c. The Coriolis effect which arises from the 

 rotation of the earth and acts to the right of the 

 velocity of the iceberg in the Northern Hemi- 

 sphere. 



d. Finally there is a small force associated with 

 the slope of the sea surface which tends to move 

 the iceberg downhill. 



An iceberg moving with a uniform velocity has 

 no net force acting on it; all forces balance. 

 When one of the forces change, the iceberg ac- 

 celerates or decelerates until a new equilibrium 

 of forces is obtained. The net force can be deter- 

 mined by the change of the drift vector over 

 some time interval. 



At the same time that the drift of the iceberg 

 is measured, measurement of wind, calculation 

 of the geostrophic current, and the surface cur- 

 rent intergrated over the depth of the iceberg 

 must be made. The force exerted by a fluid on 

 an immersed body is a function of both the drag 

 of the fluid on the body and of the square of the 

 velocity of the object relative to the fluid. Since 

 the iceberg is affected by both air and water, 

 there are two drag terms. If these drag coeffi- 

 cients are determined from the experimental data, 

 then for a given wind velocity, the velocity of the 

 wind driven surface current and the velocity of 

 the iceberg can be calculated by integrating the 

 drag forces over a time period necessary to reach 

 equilibrium. 



REFERENCES 



Budinger, T. F., 1960: Wind Effect on Icebergs. (U.S. 



Coast Guard, unpublished manuscript). 

 Ettle, Robert E., 1974: Statistical Analysis of Observed 



Iceberg Drift. Arctic 27 (2) : 121-127. 

 Kollmeyer, R. C, R. M. O'Hagan and R. M. Morse, 1965 : 



Oceanography of the Grand Banks Region and the 



Labrador Sea in 1964. U.S. Coast Guard, Oceano- 



graphic Report No. 10. 



20 



