5„ Transfer of heat over large areas 



Climates of great, populated areas such as northern Europe are 

 controlled by the current systems of the oceans. 



6. Movement of submerged objects 



The effects of currents on the movement or burial of sub- 

 merged objects are only partially understood but are known to be 

 of considerable practical importance, 



7. Ice movements 



Currents, together with winds, are of primary consideration 

 in predicting the movements of ice fields and icebergs. 



8. Surface navigation 



Detailed, prior knowledge of currents in dangerous waterways 

 is essential. Ship routes for decades have been planned to make 

 maximum use of favorable currents. 



9. Erosion 



Bottom erosion and accretion caused by currents require con- 

 stant hydrographic surveillance of all navigable waterways. 



10. Biological productivity 



The transport of nutrients, oxygen, and waste materials to and 

 away from organisms and the distribution of populations, spores, and 

 eggs are all directly related to currents. 



The accuracies in speed and direction required for determining 

 some of the above relationships vary, but in general are about ±0.1 

 knot and ±10° True. Current measuring instruments ideally should 

 have a range of 0.1 to 10.0 knots, but a range of 0.1 to 5.0 knots is 

 considered adequate for 99 percent of the oceans; lower thresholds, 

 however, may be desired for special purposes. These instruments 

 ideally should be unlimited by depth and should allow the measure- 

 ment of current gradients with depth. Most important of all, instru- 

 ments should be simple, rugged, and maintenance-free. 



VI- 2 



