VI. CURRENT MEASUREMENTS 



Quick Carlson 



A. INTRODUCTION* 



An ocean current generally is defined as a horizontal movement 

 of water and may be described at any point in time and place by a 

 vector. This vector comprises speed or "drift" in knots as its magni- 

 tude and "set" in degrees clockwise from North as its direction. 

 Currents may be divided for convenience into groups according to 

 their causal factors: (1) Currents related to density distribution, 

 (2) tidal currents, (3) currents caused by wind stress, (4) currents 

 caused by surface waves, and (5) currents caused by river outflow. 



Currents may well be the most important dynamic variable in the 

 ocean. Many phenomena are critically controlled by the current 

 behavior. These include: 



1 „ Submarine navigation 



Subsurface dead reckoning requires reliable information on deep 

 currents. 



2. Sound propagation 



Sound transmission is considerably more complicated in areas 

 of turbulence and motion. 



3. Thermal structure prediction 



Predictions of thermal gradients for sonar operations will 

 be uncertain until the term of advection due to currents can be under- 

 stood properly and predicted. 



4. Dispersal of nuclear wastes 



Effluent from atomic shore installations and atomic powered 

 ships and radioactive by-products from nuclear explosions at sea 

 must be distributed by the natural current forces in the ocean. Areas 

 of lethal accumulations must be predicted in advance. 



* Much of the material in this section was extracted from the ex- 

 tremely comprehensive report cited as Reference VI- 1 at the end of 

 this Section. 



VI-1 



