seasonal and other variations the oceanographer 

 faces problems in the geographical and time 

 spacing of the observations; this difficulty is a 

 manifestation of our ignorance of the spectrum of 

 variations in the sea's motions. The National 

 Academy of Sciences Committee on Ocean- 

 ography has stated:'^ 



TTie classical oceanographic cruise is inadequate to 

 sample the high-frequency and small-scale 

 phenomena, and oceanographic expeditions are 

 generally not long enough or extensive enough to 

 sample the low-frequency or large-dimension phe- 

 nomena. 



Data provided by moored buoys have improved 

 our understanding of the time distribution of 

 horizontal motion, but little in spatial variations. 

 Transient inertial currents account for a large 

 fraction of the kinetic energy. For periods shorter 

 than 12 hours (corresponding to horizontal dimen- 

 sions of 10 kilometers or less), the energy density 

 of velocity fluctuations decreases with frequency. 

 Vertical scales are not known. 



Considerable statistical similarity of the velocity 

 fluctuations is found in this frequency range at all 

 depths and locations sampled. The energy content 

 at frequencies below one cycle per day tends to 

 increase with decreasing frequency, but the knowl- 

 edge of temporal and spatial distribution is scanty. 

 The requirement for long-term records from many 

 sampling points has made the larger-scale low- 

 frequency portion of the spectrum relatively in- 

 accessible. '^ 



Data collected by research and survey ships along 

 "standard sections" can supplement arrays of 

 fixed current meters. NASCO has indicated that 

 standard sections can be designed with the aid of 

 measurements from anchored instruments and 

 periodic series of ship observations.''' The Coast 

 Guard has established standard oceanographic sec- 

 tions in the North Atlantic and North Pacific 

 Oceans to provide information on the seasonal and 



12 



Committee on Oceanography, National Academy of 

 Sciences-National Research Council, Oceanography 

 1966 -Achievements and Opportunities, NAS-NRC, Wash- 

 ington, D.C. (1967). 



'hbid. 



'^Ibid. 



longer-term variations in the flow of the major 

 current systems. Data is collected by Coast Guard 

 ships en route to ocean stations, as well as by Coast 

 Guard oceanographic vessels; additional data is 

 provided by Canada. These measurements are 

 usually made on a seasonal basis— four times per 

 year. Recently, the Pacific sections have been 

 sampled almost monthly. The data collected in- 

 clude temperature and salinity down to 1,500 

 meters, or the bottom, whichever is lesser, with 

 intervals selected on the basis of the dynamic 

 gradient. 



Ml. DYNAMICS OF OCEAN CURRENTS 



The general positions of the ocean's major 

 current systems have been fairly weU established 

 for more than 50 years. As more detailed observa- 

 tions are made of the current systems, however, 

 more is learned about their non-uniformity. Re- 

 cent observations have shown, for example, a 

 highly complex structure for the pattern of ocean 

 currents near the Equator in all oceans. The 

 general driving force of the ocean's current sys- 

 tems are the more-or-less permanent atmospheric 

 wind systems, combined with the earth's rotation. 

 This response, and the relationship of the fluctua- 

 tions of the ocean currents to the turbulent 

 character of the atmosphere's wind, are poorly 

 understood. Ocean currents are roughly the 

 equivalent of atmospheric-wind systems, on an 

 ocean-wide scale, with a degree of persistence, 

 month after month, not characteristic of the 

 corresponding atmospheric circulation. The gen- 

 eral direction of the major current systems' flow is 

 easily predicted. The meridional advection of heat 

 by persistent ocean currents is a major influence 

 on global climate. 



Additional data is required to define the de- 

 tailed structure of the current systems; this must 

 be coupled with basic research into the atmo- 

 spheric wind-ocean current energy exchange as 

 well as studies of bottom effects on ocean cur- 

 rents. Research efforts have achieved computer 

 simulations of the major features of the atmo- 

 sphere's general circulation and the ocean's broad 

 current features. 



IV. BIOLOGICAL PREDICTION 



Man's increasing dependence on food resources 

 from the sea and his growing capacity to modify 



n-49 



333-093 O - 69 - 



