Conservative behavior of uranium vs. salinity in Arctic sea ice and brine

The conservative behavior of uranium (U) with respect to salinity in open ocean waters is widely accepted. However, in low salinity oceanic environments, such as estuaries, its behavior seems more variable and information on its distribution over broad salinity scales still needs to be further documented. Sea ice formation in polar oceans constitutes a natural mechanism concentrating dissolved seawater constituents into high salinity brine through the distillation of "pure" water into sea ice. Here we present relative U-concentration data in fifteen samples from the Arctic Ocean. They include low-salinity sea ice, underlying surface seawater and sea ice brine covering a salinity range of ~ 0 to 135. Results suggest that U vs. salinity exhibits conservative behavior over the whole range of salinity investigated. In addition, δ234U measurements agree well with the mean oceanic 234U/238U ratio, suggesting that the processes of sea ice formation and melt do not affect the oceanic relationship between the 234U and 238U.

► Uranium concentrations are conservative across a large range of salinity.
► Arctic sea ice is a good environment to investigate the salinity effect.
► All measured uranium concentrations are equivalent to the mean ocean value if normalized to a salinity of 35.
► The sea ice formation process does not influence the 234U/238U equilibrium.