Anthropogenic radioactivity in the nordic seas and the arctic ocean — results of a joint project

The paper presents the results of a joint project combining numerical model studies and field work in order to investigate the dispersion of anthropogenic radioactivity in the Arctic Ocean. The results obtained underline the essential difference between the dispersion of dissolved contaminants in water and the transport of particulate material in sea ice. Coupled ice-ocean models on different spatial scales are applied to study the transit times and major pathways for radioactive contaminant transport in the water column. One of the main sources for radioactive pollution in the Arctic, the discharge of the Sellafield reprocessing plant, was simulated from 1965 until now. The results are compared with measurements and hypothetical release scenarios computed for the the dump sites of radioactive waste in the Kara Sea. Our comparison reveals that the Sellafield signal is by one or two orders of magnitude higher than any potential contamination from Kara Sea dump sites, even if a ’worst case’ scenario is assumed. In order to assess the role of sea ice in contaminant transport, sedimentological data from the Kara Sea and the Arctic Ocean were analysed. The results show that fine-grained Kara Sea sediments from dump site areas are predestined for entrainment into newly forming ice. Observed buoy drifts and simulated trajectories confirm that the Arctic Transpolar Ice Drift is a rather short pathway for pollutant dispersion from the Arctic Ocean to the adjacent Nordic Seas. However, compared to the large volume and contaminant flux in the ocean, the contaminant dispersion by sea ice plays a minor role.