The results of research on marine contamination in the regional areas (the Kara and Barents Seas) in the Arctic Ocean were reported at the Journal of the Japan Society for Marine Survey and Technology, Vol. 15(2).
In the present research, the authors carried out flow analysis and concentration analysis of radioactive materials in the whole region of the Arctic Ocean, based on the release scenario.
A numerical hybrid box model was developed. The results obtained agreed with the observed features in many respects. Especially, stream flows in Norwegian, Barents Sea and Kara Sea showed fairly realistic features. The flow field in the surface layer in the central Arctic Ocean agreed with that in previously known data.
In nuclide dispersion model, nuclide decay, mixing, scavenging and interaction between seawater and bottom sediment layers were taken into consideration in order to improve accuracy of the dosage estimate.
Based on nuclide (Pu-239 and Cs-137) release scenarios, the whole Arctic Ocean was subjected to analysis.
A clear difference was recognized in the diffusion distribution according to the properties of nuclides, and concentration in the sediment is one or two orders higher than that in the seawater when the distribution factor of K_d value is large as in Pu-239.

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A remotely operated vehicle (ROV) was used to observe a sound scattering layer (SSL) identified using a quantitative echo sounder near the mouth of Funka Bay, Hokkaido. The SSL was seen in a high frequency (100kHz) echogram to occur within 5 m of the sea floor. Video images taken by the ROV showed a dense school of krill swimming rapidly and continuously within the SSL. Furthermore, several walleye pollock were observed to approach the ROV at depths where relatively strong echoes appeared in a low frequency (25kHz) echogram. The density and size of the krill and walleye pollock were not determined, however, it is clear that ROVs are useful for observing the SSL and can provide valuable information about the biomass of marine resources more accurately.

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