Modeling the marine chromium cycle: new constraints on global-scale processes
Chromium (Cr) and its isotopes hold great promise as a tracer of past oxygenation and marine biological activity due to the contrasted chemical properties of its two main oxidation states, Cr(III) and Cr(VI), and the associated isotope fractionation during redox transformations. However, to date the...
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ftcopernicus:oai:publications.copernicus.org:bg94208 2023-05-15T15:13:42+02:00 Modeling the marine chromium cycle: new constraints on global-scale processes Pöppelmeier, Frerk Janssen, David J. Jaccard, Samuel L. Stocker, Thomas F. 2021-10-07 application/pdf https://doi.org/10.5194/bg-18-5447-2021 https://bg.copernicus.org/articles/18/5447/2021/ eng eng doi:10.5194/bg-18-5447-2021 https://bg.copernicus.org/articles/18/5447/2021/ eISSN: 1726-4189 Text 2021 ftcopernicus https://doi.org/10.5194/bg-18-5447-2021 2021-10-11T16:22:28Z Chromium (Cr) and its isotopes hold great promise as a tracer of past oxygenation and marine biological activity due to the contrasted chemical properties of its two main oxidation states, Cr(III) and Cr(VI), and the associated isotope fractionation during redox transformations. However, to date the marine Cr cycle remains poorly constrained due to insufficient knowledge about sources and sinks and the influence of biological activity on redox reactions. We therefore implemented the two oxidation states of Cr in the Bern3D Earth system model of intermediate complexity in order to gain an improved understanding on the mechanisms that modulate the spatial distribution of Cr in the ocean. Due to the computational efficiency of the Bern3D model we are able to explore and constrain the range of a wide array of parameters. Our model simulates vertical, meridional, and inter-basin Cr concentration gradients in good agreement with observations. We find a mean ocean residence time of Cr between 5 and 8 kyr and a benthic flux, emanating from sediment surfaces, of 0.1–0.2 nmol cm −2 yr −1 , both in the range of previous estimates. We further explore the origin of regional model–data mismatches through a number of sensitivity experiments. These indicate that the benthic Cr flux may be substantially lower in the Arctic than elsewhere. In addition, we find that a refined representation of oxygen minimum zones and their potential to reduce Cr yield Cr(III) concentrations and Cr removal rates in these regions in much improved agreement with observational data. Yet, further research is required to better understand the processes that govern these critical regions for Cr cycling. Text Arctic Copernicus Publications: E-Journals Arctic Biogeosciences 18 19 5447 5463 |
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English |
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Chromium (Cr) and its isotopes hold great promise as a tracer of past oxygenation and marine biological activity due to the contrasted chemical properties of its two main oxidation states, Cr(III) and Cr(VI), and the associated isotope fractionation during redox transformations. However, to date the marine Cr cycle remains poorly constrained due to insufficient knowledge about sources and sinks and the influence of biological activity on redox reactions. We therefore implemented the two oxidation states of Cr in the Bern3D Earth system model of intermediate complexity in order to gain an improved understanding on the mechanisms that modulate the spatial distribution of Cr in the ocean. Due to the computational efficiency of the Bern3D model we are able to explore and constrain the range of a wide array of parameters. Our model simulates vertical, meridional, and inter-basin Cr concentration gradients in good agreement with observations. We find a mean ocean residence time of Cr between 5 and 8 kyr and a benthic flux, emanating from sediment surfaces, of 0.1–0.2 nmol cm −2 yr −1 , both in the range of previous estimates. We further explore the origin of regional model–data mismatches through a number of sensitivity experiments. These indicate that the benthic Cr flux may be substantially lower in the Arctic than elsewhere. In addition, we find that a refined representation of oxygen minimum zones and their potential to reduce Cr yield Cr(III) concentrations and Cr removal rates in these regions in much improved agreement with observational data. Yet, further research is required to better understand the processes that govern these critical regions for Cr cycling. |
format |
Text |
author |
Pöppelmeier, Frerk Janssen, David J. Jaccard, Samuel L. Stocker, Thomas F. |
spellingShingle |
Pöppelmeier, Frerk Janssen, David J. Jaccard, Samuel L. Stocker, Thomas F. Modeling the marine chromium cycle: new constraints on global-scale processes |
author_facet |
Pöppelmeier, Frerk Janssen, David J. Jaccard, Samuel L. Stocker, Thomas F. |
author_sort |
Pöppelmeier, Frerk |
title |
Modeling the marine chromium cycle: new constraints on global-scale processes |
title_short |
Modeling the marine chromium cycle: new constraints on global-scale processes |
title_full |
Modeling the marine chromium cycle: new constraints on global-scale processes |
title_fullStr |
Modeling the marine chromium cycle: new constraints on global-scale processes |
title_full_unstemmed |
Modeling the marine chromium cycle: new constraints on global-scale processes |
title_sort |
modeling the marine chromium cycle: new constraints on global-scale processes |
publishDate |
2021 |
url |
https://doi.org/10.5194/bg-18-5447-2021 https://bg.copernicus.org/articles/18/5447/2021/ |
geographic |
Arctic |
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Arctic |
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Arctic |
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Arctic |
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eISSN: 1726-4189 |
op_relation |
doi:10.5194/bg-18-5447-2021 https://bg.copernicus.org/articles/18/5447/2021/ |
op_doi |
https://doi.org/10.5194/bg-18-5447-2021 |
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Biogeosciences |
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18 |
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19 |
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5447 |
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5463 |
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