DRAFT
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nd
Vertical mixing is inhibited at the thermocline due to
the stability associated with the rapid increzse in density
with depth.
Vertical mixing requires the vertics1 novement
of parcels of water.
where vertical density gradicnts are
great, as they are in the thermocline, these movements involve
relatively large amounts of energy and are therefore less
probable.
Mixing, therefore, is less.3
In the wIGWJAM opera-
tion (deep underwater atomic detonation off California) radio-
activity was materially concentrated in thin stratified layers
of high stability.
These sheets of radioactive water had
horizontal dimensions measured in miles and tens cf niles with
vertical thickness of only a few meters (except above the
thermocline).
Contamination existed in the depth of the
4
thermocline and below it at (VIGVA4 because it was introduced
at these levels.
This is contrasted with fallout which is
spread on the surface and remains mostly above the thermocline,
but sIGVYAN is the best known example to illustrate
the degree
of stratification of waters ot layers of high stability.
Computations cf stability have been made for the data
taken on the HORIZON's cruise in the PPG erea.
Fig. 11 shows
the average stability of the wost stable 25 uete> leyer, and
Fige 12 fives the cepth of the layer.
-—
3-
=
ef
le
-—
=e
we
ere
ee
—
The stability values
ee
we
Pehle
le
Since the downward penetration of radioactivity in solution
in the water is very slow at the thermocline, sunmarines may
generally avoid water with high activity by diving into the
middle of the thermocline.
Surface vessels muy obtain rele-
tively clean water for their evaporators by punping water
from within the thermocline depth zone. With a depressor on
the end of a water line the latter might be acecmplished
at normal speed.
(At early times or during fallout, clean
water undoubtedly exists in a ship's wake; therefore, a
ship probably may obtain clean water for wash-Jown by
traveling in a wide circle, or by following another vessel4
at some distance.
- Isaacs.)
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