that the vessel traversed the north equatorial
current at three distances west of Bikini,
In
the course of these traverses, the Japanese
sclentists obtained water samples at various
depths and from their data have constructed the
profiles showing contamination with depth at each
of their traverses, These profiles are attached
as Exhibit B.
3, The Japanese data are consistent with our
data obtained during CASTLE which indicate that
giffusion occurs rapidly between the surface and the
thermocline but that exchange with water below the
thermociine takes place very slowly.
Moreover,
tritium measurements of ocean water by Dr. Willard
F, Libby, while at the University of Chicago, suggest
that material distributed between the surface and
thermocline are diffused with a halflife of about 18
years,
‘This exceedingly slow rate is explained ty
the surprisingly small coefficient of exchange across
the thermocline.
h, The Japanese data also suggest that lateral
diffusion from the equatorial current is likewise
proceeding at a slower rate then would have been
expected on the basis of previously available
knowledge,
5. The Japanese data have been reviewed by oceanographers from the Woods Hole and Scripps Institute of
Oceanography and the AEC technical staff. In their
opinion a large part of the radioactivity observed in
the North Equatorial current will eventually flow
into the Kuroshio current in the manner illustrated
in Exhibit C which projects the course of this
activity for the next few months.
The diminution in
activity between the end of June when the Japanese
made their last survey and 1 March 1955 would be in
the order of 90% due to radiological decay and oceanographic factors,
This presents us with the
. possibility that large masses of the equatorial and
Kuroshio current
amounts which do
hazard but which
the attention of
may continue to be radioactive in
not necessarily constitute a health
are certainly high enough to attract
Japanese scientists.
6, The radioactivity of the Kuroshio current to the
west and north of Guam should be assessed.
In order
to facilitate monitoring of these waters an appropriate
vessel is needed to sail frem Guam on or shortly after
1 March 1955 on a reconnaissance of Far Eastern waters
for a duration of two to four weeks,
We would assign
six scientists to this vessel and would make available
certain laboratory equipment by which semples could be
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Enclosure
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ebteined and their significance assessed on a current
basis.
Tne course of the vessel should approximate
that shown in Exhibit C but operational flexibility
should be provided end the actual course determined by
the day to day research findings of the scientific
staff assigned to the mission,