Barium and Carbon fluxes in the Canadian Arctic Archipelago

Seasonal and spatial variability of dissolved Barium (Ba) in Amundsen Gulf, southeastern Beaufort Sea, was monitored over a full year from September 2007 to September 2008. Dissolved Ba displays a nutrient-type behavior: the maximum water column concentration is located below the surface layer. Highest Ba concentrations are typically observed at river mouths, the lowest concentrations are found in water masses of Atlantic origin. Barium concentrations decrease eastward through the Canadian Arctic Archipelago. Barite (BaSO4) saturation is reached at the maximum concentrations of dissolved Ba in the subsurface layer, whereas the remaining water column is undersaturated. A three end-member mixing model comprising freshwater from sea-ice melt and rivers, as well as upper halocline water, was used to establish their relative contributions to the Ba concentrations in the upper water column of the Amundsen Gulf. Based on water column and riverine Ba contributions, we assess the depletion of dissolved Ba by formation and concomitant sinking of biologically bound Ba (bio-Ba), from which we derive an estimate of the carbon export production. In the upper 50 m of the water column of Amundsen Gulf, riverine Ba accounts for up to 15% of the available dissolved Ba inventory, of which up to 20% is depleted by bio-Ba formation and export. Since riverine inputs and Ba export occur concurrently, the seasonal variability of dissolved Ba in the upper water column is moderate. Assuming a fixed organic carbon to bio-Ba flux ratio, carbon export out of the surface layer is estimated at 1.8{plus minus}0.45 mol C m‑2 yr‑1. We propose a climatological carbon budget for the Amundsen Gulf