The natural occurrence of radioactive elements 
in seawater is very small, the principal element 
being potassium-40. Man-made radioactive mate- 
rial enters the ocean by fallout. Although seawater 
greatly dilutes these wastes, some radioactive 
elements are concentrated by biological organisms. 
Ionization chambers, Geiger counters, photo- 
multiplier scintillometers, and similar instruments 
can be suspended from ships to measure radio- 
activity. 
b. Future Needs New techniques to measure 
directly temperature, salinity, and sound velocity 
to greater depths are needed to provide direct 
digital and analog output required for realtime 
data processing. 
Airborne and shipborne deep expendable re- 
cording bathythermographs for direct digital meas- 
urements of temperature versus depth to 20,000 
feet from a moving platform are needed. Direct 
measurement of sound velocity to great depths is 
required for reliable sonar operation. 
New techniques are required to permit rapid, 
continuous in situ analyses of the important 
chemical properties of seawater and bottom sedi- 
ments, particularly at sites considered for undersea 
installations. 
4. Dynamic Factors 
Ocean energy decreases with depth; therefore, 
practically all the ocean’s environmental energy is 
contained in gravity waves, tides, and currents. Yet 
other factors are important because of their 
potential hazards. 
a. Gravity Waves Predicting the exchange of 
energy and material across the air-sea interface is 
largely concerned with the growth and decay of 
gravity (wind generated) waves. This aspect has 
progressed well, making available refined forecast- 
ing techniques. Much data on average wave heights 
exist, although data still are lacking on wave 
lengths. Current research is directed primarily at 
the fundamentals of energy exchange, seeking to 
diminish the heavy reliance on observation and 
experimentation. 
Early wave observations consisted primarily of 
random visual observations from ships. Of ques- 
tionable accuracy, these data provide little knowl- 
edge of more sophisticated wave characteristics 
like spectral components, period of maximum 
energy, and directional behavior. 
Older instruments to measure sea state include 
ship’s wave recorders, photo wave recorders, wave 
poles, and stereo photogrammetry. New instru- 
ments take continuous measurements of the sea 
surface from ships, satellites, and aircraft, provid- 
ing accurate and more complete observations. 
These include (1) the airborne wave meter 
utilizing a radar altimeter device to acquire wave 
structure profiles, (2) a sonic echoing device 
mounted on a ship’s bow to measure waves 
continuously and to compensate automatically for 
ship motions, and (3) cameras on satellites (espe- 
cially in synchronous orbit) to produce photo- 
graphs analyzed for information on sea surface 
conditions. Wave sensors on fixed ocean platforms 
like the Argus Island permit study of storm waves 
not normally measured by ships. 
Subsurface wave motion, surf conditions (im- 
portant derivatives of surface waves), and such 
wave processes as generation, propagation, refrac- 
tion, decay, filtering, and subsurface pressure 
fluctuations are little understood. 
Mathematical models for computer use are 
being developed to reduce complex wave motion 
data to understandable information. The Environ- 
mental Science Services Administration is develop- 
ing mathematical models of ocean-atmosphere 
interactions and of the conveyance of heat and 
water. A more sophisticated model of total world 
hydrology, including sea ice, ground water, and 
other factors, has been developed, but its appli- 
cation is limited by lack of experimental data. 
Instrumentation to obtain pertinent data is vitally 
needed, and the technology to develop it appears 
available. 
Future wave measuring sensors must measure 
not only height but the entire directional spec- 
trum. Knowledge of waves for engineering design 
criteria is lacking. Some numerical analysis tech- 
niques have been developed for design criteria of 
the Polaris ballistic missile and other systems. 
These techniques have been amplified and im- 
proved, but the basic problem of obtaining proper 
measurements has not been solved. 
b. Internal Waves Internal waves are not well 
understood but are known to have an effect on 
underwater sound transmission. Internal waves 
usually are measured by observing short-term 
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