Cochran, J. K., D. J. Hirschberg, H. D. Livingston, K. O. Buesseler, and R. M. Key, 1995: Natural and anthropogenic radionuclide distributions in the Nansen Basin, Arctic Ocean: Scavenging rates and circulation timescales. Deep-Sea Research, Part II, 42(6), 1495-1517.

Abstract: Determination of the naturally occurring radionuclides ²³²Th, ²³⁰Th, ²²⁸Th and ²¹⁰Pb, and the anthropogenic radionuclides ²⁴¹Am, ^239,240Pu, ¹³⁴Cs and ¹³⁷Cs in water samples collected across the Nansen Basin from the Barents Sea slope to the Gakkel Ridge provides tracers with which to characterize both scavenging rates and circulation timescales in this portion of the Arctic Ocean. Large volume water samples ( ~ 1500 l) were filtered in situ to separate particulate (> 0.5 µm) and dissolved Th isotopes and ²⁴¹Am. Thorium-230 displays increases in both particulate and dissolved activities with depth, with dissolved ²³⁰Th greater and particulate ²³⁰Th lower in the deep central Nansen Basin than at the Barents Sea slope. Dissolved ²²⁸Th activities also are greater relative to ²²⁸Ra, in the central basin. Residence times for Th relative to removal from solution onto particles are ~ 1 year in surface water, ~ 10 years in deep water adjacent to the Barents Sea slope, and ~ 20 years in the Eurasian Basin Deep Water. Lead-210 in the central basin deep water also has a residence time of ~ 20 years with respect to its removal from the water column. This texture of scavenging is reflected in distributions of the particle-reactive anthropogenic radionuclide ²⁴¹Am, which shows higher activities relative to Pu in the central Nansen Basin than at the Barents Sea slope.

Distributions of ¹³⁷Cs show more rapid mixing at the basin margins (Barents Sea slope in the south, Gakkel Ridge in the north) than in the basin interior. Cesium-137 is mixed throughout the water column adjacent to the Barents Sea slope and is present in low but detectable activities in the Eurasian Basin Deep Water in the central basin. At the time of sampling (1987) the surface water at all stations had been labeled with ¹³⁴Cs released in the 1986 accident at the Chernobyl nuclear power station. In the ~ 1 year since the introduction of Chernobyl ¹³⁴Cs to the Nansen Basin, it had been mixed to depths of ~ 800 m at the Barents Sea Slope and to ~ 300 m in the central basin. "Pre-Chernobyl" inventories of ¹³⁷Cs (as well as ^{239, 240}Pu) are 10 times those expected from global atmospheric fallout from nuclear weapons testing and are derived principally from releases from the Sellafield, U.K., nuclear fuel reprocessing facility on the Irish Sea. Based on the sources of ¹³⁷Cs to the Nansen Basin, mixing time scales are 9 - 18 years for the upper water column (to 1500 m) and ~ 40 years for the deep water. These mixing time scales, combined with more rapid scavenging at the basin margin relative to the central basin, produce residence times of particle-reactive radionuclides in the Nansen Basin comparable to other open ocean areas (e.g., north-west Atlantic) despite the presence of permanent ice cover and long periods of low-light levels that limit productivity in the Arctic.