temperature fluctuations at given points in the 
water column; however, motion of the ship or 
buoy from which the instruments are suspended 
could bias results. The very stable FLIP platform 
has been used for internal wave measurements 
with good results. To predict motions in the 
environment adequately, technology is needed to 
measure three dimensional internal wave spectra 
by digital data collection techniques. 
c. Unusual Waves—Tsunamis and Hurricane Waves 
Tsunamis (tidal waves) are formed by earth- 
quakes or by slides that dislocate the ocean floor. 
They are of 200 to 300 miles in length but only 
two or three feet high in deep water. Moving at 
great speeds, they usually are not detectable to the 
eye until they increase to as much as 20 or 30 feet 
in height when approaching coastlines. 
Hurricane waves are difficult to predict because 
the circular motion of hurricane winds causes the 
waves to move at various angles from the path of 
the storm. Hurricane waves generally accompany 
storm surges or storm tides that can run 4 to 15 
feet above normal high water as they move toward 
land. Little effect from surface wave action is felt 
200 to 300 feet below the surface. 
Hurricane research is active, although a storm’s 
course cannot yet be predicted, nor its fury con- 
trolled. Technology is needed to slow the process 
of evaporation of water from the sea in a hurricane 
and to disrupt the convection process that adds 
the extra energy to convert a rain storm into a 
hurricane. Technology is needed also to develop 
improved mathematical models of storms. 
d. Thermodynamics The exchange of thermal 
energy affects the thermal structure in the upper 
ocean layers, generation of ocean weather, mainte- 
nance of global atmospheric circulation, and pro- 
pagation of perturbations in climate. Unfortu- 
nately, the process is little understood, and pro- 
gress has been slow mainly because technology is 
not developed sufficiently for the refined observa- 
tions needed to establish more effective theory. 
Ocean heat comes primarily from the sun. For 
undersea operations, however, heat flowing from 
the earth’s crust also is important (Figure 24). It is 
practically uniform on the shelf and in the basins 
but is significantly higher in areas of midocean 
ridges and trenches. Deep drilling into the crust is 
required to improve knowledge of these phenom- 
VI-68 
ena. The deep ocean depths are the coldest parts 
of the seas (3.8°C average). 
Ly 
Figure 24. Heat probe for measuring ocean bot- 
tom heat flows and taking core sample being 
lowered from oceanographic survey ship. (ESSA 
photo) 
e. Currents Surface currents are horizontal move- 
ments and include both tidal currents (produced 
by tidal movements of water in ocean basins) and 
circulation currents. Navy interest in currents 
traditionally has centered on their navigational 
effects. New developments in surface and sub- 
merged current measurements include the auto- 
matically recording deep moored telemetering 
buoy. 
Subsurface currents, important to undersea 
operations, include deep-layer vertical movements 
(upwelling or sinking) and movements caused by 
tides or large-scale turbulence. Shifts of sound 
signals is one way of measuring subsurface cur- 
rents. Long-range sonar is affected by dynamic 
changes in location and characteristics of ocean 
water masses, thus requiring extensive data on 
currents to be effective. 
However, obtaining that information in deep 
water is so expensive and time consuming that few 
measurements have been made. A few moored 
current meter arrays have been installed at the 
Navy’s Atlantic Undersea Test and Evaluation 
Center and elsewhere. Variations in current are 
computed from data taken from these arrays 
