Barium-isotopic fractionation in seawater mediated by barite cycling and oceanic circulation

Horner, Tristan J.; Kinsley, Christopher W.; Nielsen, Sune G.

doi:10.1016/j.epsl.2015.07.027

Cited by 131 publications

(279 citation statements)

References 43 publications

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“…However, these observations do not address the mechanisms behind the similar depth profiles of [Ba] and Si(OH) 4 , which have been proposed to relate to the similar remineralisation depths of their respective carrier phases (BaSO 4 and opal, respectively; e.g. Broecker and Peng, 1982), or are perhaps due to the lateral advection and circulation of conservative nutrients (Horner et al, 2015) with a Ba/Si ratio set by surface processes in the high-latitudes where the water masses form (Sarmiento et al, 2004). Although advected and organic matter-derived nutrients are traditionally labelled 'preformed' and 'regenerated' respectively, here we instead use the terms 'conservative' and 'non-conservative' to refer to these two components of Ba distributions.…”

Section: Introductionmentioning

confidence: 93%

“…Seawater collection and processing procedures for samples from the South Atlantic (D357/GA10E; Oct-Nov 2010) are discussed in Horner et al (2015). Samples from the tropical North Atlantic (JC094; Oct-Nov 2013) were collected using Niskin bottles attached to a CTD rosette system, filtered cleanly through a 0.2 micron Acropak filter (Pall Life Sciences) and samples for Ba analysis were acidified (0.1 % v/v; pH % 2.0) the same day using concentrated hydrochloric acid (HCl Romil UpA).…”

Section: Sample Collectionmentioning

confidence: 99%

“…Hence, the information provided by seawater Ba isotopes, when used in combination with [Ba], can shed light on whether variations in [Ba] are driven by conservative mixing of different water masses or by non-conservative barite cycling, including both the formation and dissolution of particles via lateral and vertical transport. Only a few data exist for the isotopic composition of barium in seawater (Horner et al, 2015;Cao et al, 2016), and they show that isotopic variations reflect a combination of ocean circulation and barite cycling, with the latter evidenced by the presence of Badepleted, isotopically-heavy subsurface waters. A South Atlantic profile showed that, in the deep ocean, Ba isotope values are largely a function of the circulation of major water masses falling on a conservative mixing line between Antarctic Intermediate Water (AAIW), North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW), with end-members likely determined by barite cycling in high latitude surface waters (Horner et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

“…Only a few data exist for the isotopic composition of barium in seawater (Horner et al, 2015;Cao et al, 2016), and they show that isotopic variations reflect a combination of ocean circulation and barite cycling, with the latter evidenced by the presence of Badepleted, isotopically-heavy subsurface waters. A South Atlantic profile showed that, in the deep ocean, Ba isotope values are largely a function of the circulation of major water masses falling on a conservative mixing line between Antarctic Intermediate Water (AAIW), North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW), with end-members likely determined by barite cycling in high latitude surface waters (Horner et al, 2015). A Ba isotope profile from the East China Sea illustrated that freshwater input can also influence the Ba isotopic composition of near-surface seawater, with Ba cycling in the upper water column dominated by the removal of lighter isotopes onto particles (Cao et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

“…Barium stable isotope analysis provides a new and powerful approach for investigating Ba cycling in seawater (Horner et al, 2015;Cao et al, 2016), as isotopic tracers are sensitive to ocean mixing and biogeochemistry: the precipitation of barite -a non-conservative process -preferentially incorporates the lighter isotopes of Ba (Von Allmen et al, 2010;Bö ttcher et al, 2012;Miyazaki et al, 2014;Nan et al, 2015), rendering residual waters depleted in Ba and isotopically 'heavier' than before precipitation occurred. In contrast, ocean mixing -a conservative process -does not fractionate isotopic distributions; resultant concentrations and isotopic patterns follow predictable isotopic mixing schemes (Hoefs, 2015).…”

Section: Introductionmentioning

confidence: 99%

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Barium isotopes reveal role of ocean circulation on barium cycling in the Atlantic

Bates

Hendry

Pryer

et al. 2017

Geochimica et Cosmochimica Acta

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134

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We diagnose the relative influences of local-scale biogeochemical cycling and regional-scale ocean circulation on Atlantic barium cycling by analysing four new depth profiles of dissolved Ba concentrations and isotope compositions from the South and tropical North Atlantic. These new profiles exhibit systematic vertical, zonal and meridional variations that reflect the influence of both local-scale barite cycling and large-scale ocean circulation. Epipelagic decoupling of dissolved Ba and Si reported previously in the tropics is also found to be associated with significant Ba isotope heterogeneity. As such, we contend that this decoupling originates from the depth segregation of opal and barite formation but is exacerbated by weak vertical mixing. Zonal influence from isotopically-'heavy' water masses in the western North Atlantic evidence the advective inflow of Ba-depleted Upper Labrador Sea Water, which is not seen in the eastern basin or the South Atlantic. Meridional variations in Atlantic Ba isotope systematics below 2000 m appear entirely controlled by conservative mixing. Using an inverse isotopic mixing model, we calculate the Ba isotope composition of the Ba-poor northern end-member as +0.45 ‰ and the Ba-rich southern end-member +0.26 ‰, relative to NIST SRM 3104a. The near-conservative behaviour of Ba below 2000 m indicates that Ba isotopes can serve as an independent tracer of the provenance of northern-versus southern-sourced water masses in the deep Atlantic Ocean. This finding may prove useful in palaeoceanographic studies, should appropriate sedimentary archives be identified, and offers new insights into the processes that cycle Ba in seawater.

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Section: Introductionmentioning

confidence: 93%

Section: Sample Collectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Barium isotopes reveal role of ocean circulation on barium cycling in the Atlantic

Bates

Hendry

Pryer

et al. 2017

Geochimica et Cosmochimica Acta

Self Cite

134

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Untangling biogeochemical processes from the impact of ocean circulation: First insight on the Mediterranean dissolved barium dynamics

Jullion

Jacquet

Tanhua

2017

Global Biogeochemical Cycles

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Reproducibility of Ba/Ca variations recorded by northeast Pacific bamboo corals

et al. 2017

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Trace elemental ratios preserved in the calcitic skeleton of bamboo corals have been shown to serve as archives of past ocean conditions. The concentration of dissolved barium (BaSW), a bioactive nutrientlike element, is linked to biogeochemical processes such as the cycling and export of nutrients. Recent work has calibrated bamboo coral Ba/Ca, a new BaSW proxy, using corals spanning the oxygen minimum zone beneath the California Current System. However, it was previously unclear whether Ba/Cacoral records were internally reproducible. Here we investigate the accuracy of using laser ablation inductively coupled plasma mass spectrometry for Ba/Cacoral analyses and test the internal reproducibility of Ba/Ca among replicate radial transects in the calcite of nine bamboo corals collected from the Gulf of Alaska (643–720 m) and the California margin (870–2054 m). Data from replicate Ba/Ca transects were aligned using visible growth bands to account for nonconcentric growth; smoothed data were reproducible within ~4% for eight corals (n = 3 radii/coral). This intracoral reproducibility further validates using bamboo coral Ba/Ca for BaSW reconstructions. Sections of the Ba/Ca records that were potentially influenced by noncarbonate bound Ba phases occurred in regions where elevated Mg/Ca or Pb/Ca and coincided with anomalous regions on photomicrographs. After removing these regions of the records, increased Ba/Cacoral variability was evident in corals between ~800 and 1500 m. These findings support additional proxy validation to understand BaSW variability on interannual timescales, which could lead to new insights into deep sea biogeochemistry over the past several centuries.

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Barium-isotopic fractionation in seawater mediated by barite cycling and oceanic circulation

Cited by 131 publications

References 43 publications

Barium isotopes reveal role of ocean circulation on barium cycling in the Atlantic

Barium isotopes reveal role of ocean circulation on barium cycling in the Atlantic

Untangling biogeochemical processes from the impact of ocean circulation: First insight on the Mediterranean dissolved barium dynamics

Reproducibility of Ba/Ca variations recorded by northeast Pacific bamboo corals

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