New insights into global barium cycling from the first barium isotope data for seawater

A new method developed by Horner and co-workers (2015, see reference below) allows for the determination of dissolved barium (Ba) isotopic compositions in seawater using nanogram quantities of Ba.

The formation of BaSO4 (barite) in open ocean seawater is largely driven by the microbial remineralization of sinking organic matter. By analysing a 4500 m depth profile of Ba-isotopic compositions from the South Atlantic, Horner et al. find that BaSO4 precipitation removes isotopically light Ba from seawater, which renders residual, Ba-depleted seawater with heavier Ba-isotopic compositions. The distinct patterns of Ba isotopic variation in the deep ocean are clearly related to the mixing of distinct water masses formed at higher latitudes. These data indicate that water masses obtain their Ba-isotopic signatures when at or near the near-surface, and that regional circulation exerts a strong control over Ba-isotopic distributions in the South Atlantic, and possibly elsewhere.

More broadly, these new data point to several important linkages between C remineralization and the Ba cycle, suggesting that Ba-isotopes may develop into a powerful new means to study marine biogeochemical cycles.

15 Horner Barium l

Figure: Horner et al. present the first Ba-isotopic analyses of seawater for samples collected as part of UK GEOTRACES from the South Atlantic (GA10E/D357; see inset for location). The profile shows substantial Ba-isotopic variation (left) that correlates with the major changes in Ba concentrations (right). The concentrations and isotopic data reflect a combination of both barite cycling in the shallow subsurface and large-scale oceanic circulation.

Reference :

Horner, T. J., Kinsley, C. W., & Nielsen, S. G. (2015). Barium-isotopic fractionation in seawater mediated by barite cycling and oceanic circulation. Earth and Planetary Science Letters, 430, 511-522. Click here to access the paper.

Latest highlights

Science Highlights

Rare Earth Elements and neodymium isotopes as tracers in the Mediterranean Sea

Garcia-Solsona and co-workers analysed 9 seawater stations around the central Mediterranean Sea…


Science Highlights

A new model simulates the speciation and dispersion of hydrothermal iron

Roshan and collaborators present new observations of dissolved iron and its physical speciation in the South Pacific


Science Highlights

Mechanisms driving biological CO2 drawdown in the Subarctic Pacific unraveled

Nishioka and co-authors compiled comprehensive data sets of iron and macronutrients covering the whole subarctic Pacific…


Science Highlights

The biogeochemical ventures of dissolved iron and manganese across the Arctic Ocean

The spatial distributions and biogeochemical cycling of dissolved Fe (dFe) and dissolved manganese (dMn) across the Arctic Ocean were established during summer and fall 2015. The Canadian GEOTRACES transect extended from the Canada Basin (CB) to the Labrador Sea (LS) via the Canadian Arctic Archipelago (CAA). The surface, subsurface and deep water distributions for both […]