Cesium-137 concentrations at CESAR decreased from a mean value of 4.2 Bq/m 3 in the surface mixed layer to less than 1.0 Bq/m 3 in the Atlantic layer and deep waters. Cesium-137 concentrations were similar to CESAR values in the surface mixed layer at the Ice Island, but in halocline water they were lower than values measured at comparable water depths at CESAR. The data are consistent with mixing occurring over the Russian continental shelves followed by lateral advection through the interior halocline waters of the Canada Basin. Dissolved 2 1 0 Pb and 2 1 0 Po concentrations were higher in nutrient maximum water at the Ice Island compared to CESAR. Plutonium-239,240 is also depleted, relative to 1 3 7 Cs in the surface mixed layer and upper halocline at the Ice Island owing to its scavenging during modification of Pacific water in shelf environments. The 2 3 9 , 2 4 0 Pu 1 3 7 Cs ratio increases to values approaching fallout levels in lower halocline and Atlantic water owing to both reduced 2 3 9 , 2 4 0 Pu removal in source waters and vertical transport of 2 3 9 , 2 4 0 Pu with sinking particles.