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The key features of the large-scale circulation of the Arctic Ocean are reviewed based on distributions of hydrographic parameters and natural and anthropogenic trace substances. Salinity and mass balances, as well as a combination of the tracers tritium and δ 18 O, suggest a mean residence time of the shelf waters in the Siberian seas of about 3 years. Potential pathways of pollutants released to the Siberian shelf seas from the dumpsites or from river runoff are inferred from the distributions of δ 18 O and salinity. Transit times needed for dissolved contaminants to cross the central Arctic basins (several years to one or two decades in near-surface waters) and mean residence times of contaminants in the intermediate (several decades) and deep waters (several centuries) are estimated from the distribution of transient tracers (tritium and its radioactive decay product, 3 He) and “steady-state” tracers ( 14 C and 39 Ar).

Nuclear activity on land and dumping of waste in the Siberian shelf seas mean that the Kara Sea is most likely to experience inputs of radioactivity. Industrial and other anthropogenic activities in the expansive Ob' and Yenisey watersheds also contribute organochlorines, heavy metals and oil to this region. Contaminant fate is influenced by the distribution of the river discharge and processes associated with ice formation and ocean currents. Although average conditions are important in the transport of pollutants, events such as storms and iceberg gouging may be critical in deciding the ultimate fate of dumped and released contaminants.

Satellite images from the Kara Sea show that, until July, fast-ice extends along the coast and Fills the estuaries of the Ob' and Yenisey rivers. It is separated from offshore drift-ice by a region of open water, comprising a flaw lead/polynya. By August, much of the fast and drift-ice has melted and retreated from the southwestern Kara Sea, leaving behind a persistent patch of sea-ice east of Novaya Zemlya. Because both the OF and Yenisey rivers discharge water throughout the winter, the fast-ice is likely to incorporate river-borne contaminants by bottom adfreezing. During peak river discharge in June, the fast-ice remains in place, and is potentially influenced by the river outflow throughout the length of the estuary. Breakup and melting of the fast-ice in July could release contaminants to the surface waters. By late July and August, when the fast-ice has disappeared, the river discharge is observed primarily along the shore in a zone that extends offshore more than 100 km. In fall, newly-forming ice may incorporate contaminants from the river plume, while in late winter, convection penetrating to the sea floor may allow resuspended sediments to be entrained in ice forming in the flaw lead/polynya. Drift-ice formed in this region could then advect contaminants offshore. The potential for exchange of water, ice and contaminants with the Barents Sea through Karskiye Vorota, south of Novaya Zemlya, is discussed in the context of the temperature and turbidity distribution observed in the satellite images.