Rivers in the Sea 1 



By F. G. Walton Smith 



Vice President and Secretary 

 The International Oceano graphic Foundation 



[With 6 plates] 



The passenger aboard ship, out of sight of land, sees only the mo- 

 tion of his vessel through the water. There is nothing visible about 

 the sea surface to show whether the water itself is moving, either as a 

 favorable current, helping the ship's progress, or, as an adverse cur- 

 rent, retarding it. Yet currents do exist in the open sea, of such power 

 as to make a substantial difference to the daily distance made good by 

 the ship and so be important to the mariner as a factor in fuel econ- 

 omy as well as in his navigational estimates. It is important, then, to 

 measure the speed of these rivers in the sea and to know how they 

 vary from season to season, day to day, and even hour to hour. The 

 ways of doing this are surprisingly varied and involve some of the 

 most ingenious ideas and devices in the science of oceanography. 



IMPORTANCE OF CURRENTS 



There are other ways in which ocean currents are important. Near 

 the Equator the surface of the sea gains heat from the sun, whereas 

 there is a heat loss at the Poles. The action of such currents as the 

 Gulf Stream, carrying warm water poleward, has a profound effect 

 upon climate and weather. The distribution of fishes is dependent 

 upon sea-water temperature, and is thus both directly and indirectly 

 related to ocean currents. Currents not only carry food in the form 

 of microscopic sea life or plankton but also help to distribute the fer- 

 tilizer materials upon which they grow. There are numerous other 

 problems both of scientific and practical importance which involve a 

 knowledge of the pattern in water movement in the sea, and today 

 there is the most recent one of disposing of radioactive wastes at the 

 bottom of ocean deeps. This requires a knowledge of how long it 



1 Reprinted by permission from Bulletin of the International Oceanographic 

 Foundation, vol. 2, No. 2, July 1956. 



431 



