OCEANOGRAPHY IN THE UNITED STATES 277 



discovery of two new mcajor ocean currents in the past decade, one by 

 accident and the other through theoretical prediction. New under- 

 standing has also been gained of, among other things, the nature of 

 subsurface waves and of the role of sea salt in rainfall. This knowl- 

 edge is of clear benefit to our national economy even though such, or 

 any, applications were far from uppermost in the minds of the dis- 

 coverers. 



Since the time of the American Civil War many nations have con- 

 tributed to a systematic description of the physical geography of the 

 seas by sending out major expeditionary ships for periods of several 

 years. This accumulation of information has provided most of the 

 basic knowledge we have of the steady or climatological mean distri- 

 bution of oceanic properties. Three of the most searching studies of 

 the architecture of the oceans were made by the British in the Ant- 

 arctic waters in connection with the whale fishery, by an American 

 expedition extended over the whole globe under the sponsorship of 

 the Carnegie Institution of Washington and by the German Meteor 

 expedition which concerned itself mainly with the south and equatorial 

 Atlantic Oceans. During the International Geophysical Year the 

 area of the Meteor expedition was resurveyed and extended into the 

 North Atlantic. The results of these recent studies show that the 

 mean distribution of oceanic properties has not changed appreciably 

 in the course of three decades. 



This information is of fundamental significance because it is the 

 steady component of the circulations of the oceans that have, in com- 

 mon with the atmosphere, an important role to play in the maintenance 

 of the climates of the earth. As study advances it is becoming in- 

 creasingly clear that the ocean- atmosphere system will one day be 

 considered as a single problem for investigation. Wliile the at- 

 mosphere is the principal avenue along which the excess of heat 

 supplied by the sun to the equatorial regions of the earth is exported 

 toward the poles, it is the water evaporated from oceans that makes 

 this possible. Water evaporated from the sea permits the atmosphere 

 to carry heat to high latitudes in a latent rather than sensible form. 

 The efficiency of the latent heat process is approximately 50 times 

 greater than would be the case in the absence of water vapor trans- 

 port. The oceans also influence the atmospheric circulation directly 

 through their enormous heat storage capacity. 



Lately the center of gravity of research interest has shifted from 

 global surveys to a more analytical approach in which ships and men 

 go forth to find answers to carefully stated questions which their 

 research has led them to ask. Some of these concern the details of 

 the processes by which water vapor is exchanged between the oceans 

 and the atmosphere. Others relate to the unsteady motions of the 

 sea: the phenomena accompanying internal waves, the meandering, 

 pulsation, and tidal modulation of strong currents such as the Gulf 

 Stream and the dynamics of the circulation far below the surface. 

 These problems are being studied primarily because of their scien- 

 tific interest but they also liave important bearing on the industrial 

 and military uses of the ocean in much the same way that knowledge 

 of the storms and winds of the atmosphere are of importance to 

 aviation. 



