MAJOR ACCOMPUSHMENTS 69 



been measured. Much of this effort has been due to the develop- 

 ment of associated technology in buoys and sensors; in particular, 

 subsurface currents have been discovered, and several of them 

 have been the subject of major oceanographic expeditions. Other 

 subsurface currents are suspected from theoretical considera- 

 tions and need to be examined. It is also now known from ob- 

 servations that the deep waters are in constant motion, in many 

 cases with startling velocities that have modified our concepts 

 on the amount of water transport, sedimentation, and erosion 

 in the oceans. 



The theory of ocean circulation has advEinced to the point 

 where, in most cases, experimental verification is now neces- 

 sary for further advancement. In terms of the ultimate under- 

 standing of the processes which take place in the ocean, our 

 present knowledge is a bare beginning; but in terms of what was 

 known before World War 11, this knowledge is significant. 



THERMAL STRUCTURE 



Above the permanent thermocline, the temperature of the 

 ocean water is the controlling environmental factor influencing 

 the transmission of sound and the effectiveness of Navy sonar 

 systems. This layer of the ocean is also a major source of heat 

 for the atmosphere and, as such, influences the weather and, in 

 turn, most naval operations. 



Since World War II, with the advent of the bathythermograph, 

 millions of measurements of the thermal structure of the upper 

 layers of the oceans have been recorded. Many of these have 

 been obtained from research ships in the course of their studies 

 throughout the world oceans. Others have been collected by naval 

 forces for operational purposes. A large fraction of these re- 

 cordings have been analyzed and the results presented in a form 

 which is having a significant impact on naval operations. Bathy- 

 thermograph observations from the North Atlantic, North 

 Pacific, and Indian Oceans as well as the Mediterranean are 

 being digitized and, by use of high-speed computers, processed 

 to give a comprehensive picture of temperature structure in the 

 top 400 feet. 



