Barium-isotopic fractionation in seawater mediated by barite cycling and oceanic circulation
Date
2015-07-09Author
Horner, Tristan J.
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Kinsley, Christopher W.
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Nielsen, Sune G.
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https://hdl.handle.net/1912/7511As published
https://doi.org/10.1016/j.epsl.2015.07.027Keyword
Barium; Isotopic fractionation; Barite; Seawater; BiogeochemistryAbstract
The marine biogeochemical cycle of Ba is thought to be controlled by particulate BaSO4 (barite) precipitation associated
with the microbial oxidation of organic carbon and its subsequent dissolution in the BaSO4-undersaturated
water column. Despite many of these processes being largely unique to Ba cycling, concentrations of Ba and Si in
seawater exhibit a strong linear correlation. The reasons for this correlation are ambiguous, as are the depth ranges
corresponding to the most active BaSO4 cycling and the intermediate sources of Ba to particulate BaSO4. Stable
isotopic analyses of dissolved Ba in seawater should help address these issues, as Ba-isotopic compositions are
predicted to be sensitive to the physical and biogeochemical process that cycle Ba. We report a new methodology
for the determination of dissolved Ba-isotopic compositions in seawater and results from a 4, 500 m depth profile
in the South Atlantic at 39.99 S, 0.92 E that exhibit oceanographically-consistent variation with depth. These data
reveal that water masses obtain their [Ba] and Ba-isotopic signatures when at or near the surface, which relates to
the cycling of marine BaSO4. The shallow origin of these signatures requires that the substantial Ba-isotopic variations
in the bathypelagic zone were inherited from when those deep waters were last ventilated. Indeed, the water
column below 600 m is well explained by conservative mixing of water masses with distinct [Ba] and Ba-isotopic
compositions. This leads us to conclude that large scale oceanic circulation is important for sustaining the similar
oceanographic distributions of Ba and Si in the South Atlantic, and possibly elsewhere. These data demonstrate
that the processes of organic carbon oxidation, BaSO4 cycling, and Ba-isotopic fractionation in seawater are closely
coupled, such that Ba-isotopic analyses harbor great potential as a tracer of the carbon cycle in the modern and
paleo-oceans.
Description
Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters, 430 (2015): 511-522, doi:10.1016/j.epsl.2015.07.027.
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Suggested Citation
Preprint: Horner, Tristan J., Kinsley, Christopher W., Nielsen, Sune G., "Barium-isotopic fractionation in seawater mediated by barite cycling and oceanic circulation", 2015-07-09, https://doi.org/10.1016/j.epsl.2015.07.027, https://hdl.handle.net/1912/7511Related items
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Barium isotope ratios (δ138Ba) in small size fraction particles from Leg 2 (Hilo, HI to Papeete, French Polynesia) of the US GEOTRACES Pacific Meridional Transect (PMT) cruise (GP15, RR1815) on R/V Roger Revelle from Oct-Nov 2018
Horner, Tristan J. (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2021-01-14)This dataset reports barium isotope ratios (δ138Ba) in small size fraction particles Leg 2 (Hilo, HI to Papeete, French Polynesia) of the US GEOTRACES Pacific Meridional Transect (PMT) cruise (GP15, RR1815) on R/V Roger ... -
Barium isotope ratios (δ138Ba) in small size fraction particles from Leg 1 (Seattle, WA to Hilo, HI) of the US GEOTRACES Pacific Meridional Transect (PMT) cruise (GP15, RR1814) on R/V Roger Revelle from September to October 2018
Horner, Tristan J. (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2021-01-14)This dataset reports barium isotope ratios (δ138Ba) in small size fraction particles from Leg 1 (Seattle, WA to Hilo, HI) of the US GEOTRACES Pacific Meridional Transect (PMT) cruise (GP15, RR1814) on R/V Roger Revelle ... -
Barium isotope ratios (δ138Ba) in small size fraction particles from Leg 1 (Seattle, WA to Hilo, HI) of the US GEOTRACES Pacific Meridional Transect (PMT) cruise (GP15, RR1814) on R/V Roger Revelle from September to October 2018
Horner, Tristan J. (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2021-06-22)This dataset reports barium isotope ratios (δ138Ba) in small size fraction particles from Leg 1 (Seattle, WA to Hilo, HI) of the US GEOTRACES Pacific Meridional Transect (PMT) cruise (GP15, RR1814) on R/V Roger Revelle ...