Behaviour of chromium isotopes in the eastern sub-tropical Atlantic Oxygen Minimum Zone
Constraints on the variability of chromium (Cr) isotopic compositions in the modern ocean are required to validate the use of Cr isotopic signatures in ancient authigenic marine sediments for reconstructing past levels of atmospheric and ocean oxygenation. This study presents dissolved Cr concentrat...
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ftsouthampton:oai:eprints.soton.ac.uk:418689 2023-07-30T04:04:58+02:00 Behaviour of chromium isotopes in the eastern sub-tropical Atlantic Oxygen Minimum Zone Goring-Harford, Heather Klar, Jessica Pearce, Christopher Connelly, D.P. Achterberg, Eric James, Rachael 2018-03-10 text https://eprints.soton.ac.uk/418689/ https://eprints.soton.ac.uk/418689/1/Goring_Harford_et_al_GCA_2018_for_eprints.pdf en English eng https://eprints.soton.ac.uk/418689/1/Goring_Harford_et_al_GCA_2018_for_eprints.pdf Goring-Harford, Heather, Klar, Jessica, Pearce, Christopher, Connelly, D.P., Achterberg, Eric and James, Rachael (2018) Behaviour of chromium isotopes in the eastern sub-tropical Atlantic Oxygen Minimum Zone. Geochimica et Cosmochimica Acta. (doi:10.1016/j.gca.2018.03.004 <http://dx.doi.org/10.1016/j.gca.2018.03.004>). cc_by_4 Article PeerReviewed 2018 ftsouthampton https://doi.org/10.1016/j.gca.2018.03.004 2023-07-09T22:21:09Z Constraints on the variability of chromium (Cr) isotopic compositions in the modern ocean are required to validate the use of Cr isotopic signatures in ancient authigenic marine sediments for reconstructing past levels of atmospheric and ocean oxygenation. This study presents dissolved Cr concentrations (CrT, where CrT = Cr(VI) + Cr(III)) and Cr isotope data (δ53Cr) for shelf, slope and open ocean waters within the oxygen minimum zone (OMZ) of the eastern sub-tropical Atlantic Ocean. Although dissolved oxygen concentrations were as low as 44-90 μmol kg-1 in the core of the OMZ, there was no evidence for removal of Cr(VI). Nonetheless, there was significant variability in seawater δ53Cr, with values ranging from 1.08 to 1.72‰. Shelf CrT concentrations were slightly lower (2.21 ± 0.07 nmol kg-1) than in open ocean waters at the same water depth (between 0 and 160m, 2.48 ± 0.07 nmol kg-1). The shelf waters also had higher δ53Cr values (1.41 ± 0.14‰ compared to 1.18 ± 0.05‰ for open ocean waters shallower than 160m). This is consistent with partial reduction of Cr(VI) to Cr(III), with subsequent removal of isotopically light Cr(III) onto biogenic particles. We also provide evidence for input of relatively isotopically heavy Cr from sediments on the shelf. Intermediate and deep water masses (AAIW and NADW) show a rather limited range of δ53Cr values (1.19 ± 0.09‰) and inputs of Cr from remineralisation of organic material or re-oxidation of Cr(III) appear to be minimal. Authigenic marine precipitates deposited in deep water in the open ocean therefore have the potential to faithfully record seawater δ53Cr, whereas archives of seawater δ53Cr derived from shelf sediments must be interpreted with caution. Article in Journal/Newspaper NADW University of Southampton: e-Prints Soton Geochimica et Cosmochimica Acta 236 41 59 |
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Open Polar |
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University of Southampton: e-Prints Soton |
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ftsouthampton |
language |
English |
description |
Constraints on the variability of chromium (Cr) isotopic compositions in the modern ocean are required to validate the use of Cr isotopic signatures in ancient authigenic marine sediments for reconstructing past levels of atmospheric and ocean oxygenation. This study presents dissolved Cr concentrations (CrT, where CrT = Cr(VI) + Cr(III)) and Cr isotope data (δ53Cr) for shelf, slope and open ocean waters within the oxygen minimum zone (OMZ) of the eastern sub-tropical Atlantic Ocean. Although dissolved oxygen concentrations were as low as 44-90 μmol kg-1 in the core of the OMZ, there was no evidence for removal of Cr(VI). Nonetheless, there was significant variability in seawater δ53Cr, with values ranging from 1.08 to 1.72‰. Shelf CrT concentrations were slightly lower (2.21 ± 0.07 nmol kg-1) than in open ocean waters at the same water depth (between 0 and 160m, 2.48 ± 0.07 nmol kg-1). The shelf waters also had higher δ53Cr values (1.41 ± 0.14‰ compared to 1.18 ± 0.05‰ for open ocean waters shallower than 160m). This is consistent with partial reduction of Cr(VI) to Cr(III), with subsequent removal of isotopically light Cr(III) onto biogenic particles. We also provide evidence for input of relatively isotopically heavy Cr from sediments on the shelf. Intermediate and deep water masses (AAIW and NADW) show a rather limited range of δ53Cr values (1.19 ± 0.09‰) and inputs of Cr from remineralisation of organic material or re-oxidation of Cr(III) appear to be minimal. Authigenic marine precipitates deposited in deep water in the open ocean therefore have the potential to faithfully record seawater δ53Cr, whereas archives of seawater δ53Cr derived from shelf sediments must be interpreted with caution. |
format |
Article in Journal/Newspaper |
author |
Goring-Harford, Heather Klar, Jessica Pearce, Christopher Connelly, D.P. Achterberg, Eric James, Rachael |
spellingShingle |
Goring-Harford, Heather Klar, Jessica Pearce, Christopher Connelly, D.P. Achterberg, Eric James, Rachael Behaviour of chromium isotopes in the eastern sub-tropical Atlantic Oxygen Minimum Zone |
author_facet |
Goring-Harford, Heather Klar, Jessica Pearce, Christopher Connelly, D.P. Achterberg, Eric James, Rachael |
author_sort |
Goring-Harford, Heather |
title |
Behaviour of chromium isotopes in the eastern sub-tropical Atlantic Oxygen Minimum Zone |
title_short |
Behaviour of chromium isotopes in the eastern sub-tropical Atlantic Oxygen Minimum Zone |
title_full |
Behaviour of chromium isotopes in the eastern sub-tropical Atlantic Oxygen Minimum Zone |
title_fullStr |
Behaviour of chromium isotopes in the eastern sub-tropical Atlantic Oxygen Minimum Zone |
title_full_unstemmed |
Behaviour of chromium isotopes in the eastern sub-tropical Atlantic Oxygen Minimum Zone |
title_sort |
behaviour of chromium isotopes in the eastern sub-tropical atlantic oxygen minimum zone |
publishDate |
2018 |
url |
https://eprints.soton.ac.uk/418689/ https://eprints.soton.ac.uk/418689/1/Goring_Harford_et_al_GCA_2018_for_eprints.pdf |
genre |
NADW |
genre_facet |
NADW |
op_relation |
https://eprints.soton.ac.uk/418689/1/Goring_Harford_et_al_GCA_2018_for_eprints.pdf Goring-Harford, Heather, Klar, Jessica, Pearce, Christopher, Connelly, D.P., Achterberg, Eric and James, Rachael (2018) Behaviour of chromium isotopes in the eastern sub-tropical Atlantic Oxygen Minimum Zone. Geochimica et Cosmochimica Acta. (doi:10.1016/j.gca.2018.03.004 <http://dx.doi.org/10.1016/j.gca.2018.03.004>). |
op_rights |
cc_by_4 |
op_doi |
https://doi.org/10.1016/j.gca.2018.03.004 |
container_title |
Geochimica et Cosmochimica Acta |
container_volume |
236 |
container_start_page |
41 |
op_container_end_page |
59 |
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1772816618358833152 |