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FUTURE DIRECTIONS IN OCEAN SCIENCES 53 



aided by advances in measurement and computational technol- 

 ogy. Designing and deploying a global ocean observing system are 

 among the most important and difficult tasks for physical ocean- 

 ography and climate studies for the next decade. Such a system 

 would incorporate existing measurement programs as w^ell as ob- 

 servations that are not yet routine. 



Several topics will dominate physical oceanographic research 

 in the coming decade. Research in modeling, ocean mixing, ther- 

 mohaline circulation, and water mass formation processes will be 

 important. To achieve their scientific objectives and to make 

 more complete ocean observations, physical oceanographers must 

 use both proven methods and new technologies, including acous- 

 tic techniques; measurements made from volunteer observing ships; 

 satellite observations and data relay; and measurements of the 

 distributions of trace chemicals. 



Introduction 



The ocean consists of nearly 1.4 billion cubic kilometers of 

 salty water, about 97 percent of the free water on Earth. In com- 

 parison, the atmosphere holds only about 0.001 percent. This 

 volume of water exerts a powerful influence on Earth's climate by 

 transporting heat, water, and other climate-relevant properties around 

 the globe and by exchanging these properties, as well as green- 

 house gases (e.g., carbon dioxide, methane, and chlorofluorocar- 

 bons), with the atmosphere. Net ocean absorption of greenhouse 

 gases and some greenhouse-induced heat from the atmosphere can 

 delay greenhouse warming of the atmosphere. Predicting future 

 climate conditions depends on learning what controls ocean cir- 

 culation and water mass formation, and whether the system is 

 predictable, even in principle. 



Physical oceanography, like many fields of science, consists of 

 theory, observations, and numerical models. Physical oceanographic 

 theories use the equations of fluid dynamics, modified to account 

 for Earth's rotation and shape (e.g., O'Brien, 1985). A goal of 

 physical oceanography is to develop a quantitative understanding 

 of the ocean circulation, including fluxes — of energy, momentum, 

 and chemical substances — within the ocean and across its bound- 

 aries. Physical oceanographers must contribute to the increasing 

 societal emphasis on measuring, predicting, and planning for changes 

 in global climate by improving understanding of the physical fac- 

 tors that maintain the overall physical, chemical, and biological 

 characteristics of the ocean. Advances in measurement and com- 



