Distribution and inventory of 129I in the central Arctic Ocean

Abstract

The concentration of 129I was measured in water samples from three depth profiles collected in the central Arctic Ocean during 1996. The results indicate >7 × 108 atoms/liter in the cold, low salinity, 100‐m‐deep surface layer, and 0.06 × 108 atoms/liter at a depth below 3 km. The total inventory of 129I in the region is estimated at about 2.7 × 1027 atoms, representing 34% of the total discharge from Sellafield and La Hague until 1996. Marine input accounts for a major part (>90%) of the 129I inventory in the central Arctic Ocean while input from fresh water (ice melting and rivers), bomb tests and nuclear dumping contribute by about 3%. The inventory suggests a maximum marine transport time of 11 years for 129I from La Hague‐Sellafield to the central Arctic. The 129I concentration at a depth below 3 km is about one order of magnitude higher than the estimated pre‐anthropogenic global marine value, reflecting contribution from anthropogenic sources.