Barium and carbon fluxes in the Canadian Arctic Archipelago

Abstract

[1] The seasonal and spatial variability of dissolved Barium (Ba) in the 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. The 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 (BaSO 4 ) saturation is reached at the maximum dissolved Ba concentrations in the subsurface layer, whereas the rest of the water column is undersaturated. A three end-member mixing model comprising freshwater from sea-ice melt and rivers, as well as upper halocline water, is 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 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 the 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 ± 0.45 mol C m −2 yr −1. Finally, we propose a climatological carbon budget for the Amundsen Gulf based on recent literature data and our findings, the latter bridging the surface and subsurface water carbon cycles.

Absorption and fluorescence of dissolved organic matter in the waters of the Canadian Arctic Archipelago, Baffin Bay, and the Labrador Sea

“…Indeed, the LSd surface waters are formed by mixing between both low‐DOM CAA waters (Figure ) [ Walker et al ., ] and Arctic Ocean waters that have entered from the North past Smith Sound and through Nares Strait (Figure ). These southward flowing waters originate in the western Arctic Ocean and are characterized by relatively high concentrations of terrestrially derived CDOM [ Guéguen et al ., ; Walker et al ., ] and barium [ Thomas et al ., ]. The BB surface waters are influenced by the warm and saline DOM‐poor Atlantic waters entering from the south eastern part of LS (Figures and ) [ Muench , ], and the outflow of CAA through LSd and the Nares Strait.…”

Spatial segregation, dispersion and migration in early stages of polar cod Boreogadus saida revealed by otolith chemistry

“…Barium concentrations are higher in freshwater than in seawater and otolith Ba/Ca tends to accurately reflect ambient Ba/Ca (Campana 1999;Martin and Thorrold 2005). As in other oceanic regions, Ba in the Canadian Arctic displays a nutrient-type behavior with the highest surface concentrations observed at river mouths and typical profiles showing maximum concentration at the base of the surface layer decreasing above and below (Guay and Kenison Falkner 1997;Thomas et al 2011). The lowest otolith edge Ba/Ca ratios found among polar cod juveniles from Frobisher Bay may result from their ontogenetic vertical migration.…”

Spatiotemporal Variability of Barium in Arctic Sea‐Ice and Seawater

“…Seawater [Ba] values range from 38.4 to 51.3 nmol/kg, and exhibit relatively low variability and absolute values compared to previous Arctic studies (Abrahamsen et al, ; Dodd et al, ; Thomas et al, ). Despite this low variability, the [Ba] profiles still show characteristic enrichment at depth, with some subsurface peaks above the halocline (Figure ).…”

“…Furthermore, particulate barium—largely in the form of barium sulfate or barite—shows strong links with particulate organic carbon. Specifically, particulate “excess Ba” (Ba xs i.e., any Ba that is present in particles that is unsupported by lithogenic material) correlates with the flux of particulate organic carbon (POC) measured in suspended particulates (Dehairs et al, ; Thomas et al, ), sediment traps (Cardinal et al, ), and seafloor sediments (Eagle et al, ). More recent studies, including those utilizing marine barium isotopes, also highlight the nonconservative behavior of barium in near surface waters (Bates et al, ; Horner et al, ; Hsieh & Henderson, ; Jullion et al, ).…”

“…These two critical assumptions may also be questioned in the specific conditions of the Arctic, in particular as a result of biological uptake in the Arctic summer, which leads to barium drawdown associated with organic matter (Abrahamsen et al, ; Thomas et al, ). Other studies suggest that nonconservative behavior may originate in high‐latitude sea‐ice zones that are independent of silicon cycling and other indicators of biological activity (Pyle et al, ).…”