4 ¢ ce ta eee ae Bie5:rR Ea that the vessel traversed the north equatorial current at three distances west of Bikini. In the course of these traverses, the Japanese scientists obtained water samples at various depths and from their data have constructed the profiles showing contamination with depth at each of their traverses, as Exhidit B, These profiles are attached 3. The Japanese data are consistent with our data obtained during CASTLE whioh indicate that diffusion occurs rapidly between the surface and the thermocline but that exchange with water below-the thermocline 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 ard thermocline are diffused with e halflife of about 18 we eneeea 8 years, This exceedingly slow rate is exolained ty the surprisingly small coefficient of exchange across the thermocline, “ aeAeeee went. 4, The Japanese data also suggest that lateral diffusion from the equatorial current is likewise proceeding at a slower rate than 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 Scripys Institute of Oceanography and the AEC technical steff. 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 oceanographiec factors, This presents us with the possibility that large masses of the equatorial and Kuroshio current may continue to be radioactive in amounts which do not necessarily constitute a heelth hazard but which are certainly high enovgh to attract the attention of Japanese scientists, 6, The radioactivity of the Kuroshio current to the west and north of Guam snould be assessed. In order to facilitate monitoring of these waters an epprovriate vessel is needed to sail frcm Guam on or shortly efter 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 samples could be obtetned 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 and the actual’ course determined by the day to day research findings of the scientific staff assigned to the mission, x Enclosure I ue we yeOy