Improving the inverse modeling of a trace isotope: how precisely can radium-228 fluxes toward the ocean and submarine groundwater discharge be estimated?
19 pages, 9 figures, 6 tables, supplement https://doi.org/10.5194/bg-14-3171-2017 Radium-228 (228Ra), an almost conservative trace isotope in the ocean, supplied from the continental shelves and removed by a known radioactive decay (T1∕2 = 5. 75 years), can be used as a proxy to constrain shelf flux...
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ftcsic:oai:digital.csic.es:10261/219715 2024-02-11T10:00:59+01:00 Improving the inverse modeling of a trace isotope: how precisely can radium-228 fluxes toward the ocean and submarine groundwater discharge be estimated? Le Gland, Guillaume Mémery, L. Aumont, O. Resplandy, Laure 2017-07 http://hdl.handle.net/10261/219715 https://doi.org/10.5194/bg-14-3171-2017 en eng European Geosciences Union Publisher's version https://doi.org/10.5194/bg-14-3171-2017 No Biogeosciences 14: 3171-3189 (2017) 1726-4170 http://hdl.handle.net/10261/219715 doi:10.5194/bg-14-3171-2017 1726-4189 open artículo http://purl.org/coar/resource_type/c_6501 2017 ftcsic https://doi.org/10.5194/bg-14-3171-2017 2024-01-16T10:57:50Z 19 pages, 9 figures, 6 tables, supplement https://doi.org/10.5194/bg-14-3171-2017 Radium-228 (228Ra), an almost conservative trace isotope in the ocean, supplied from the continental shelves and removed by a known radioactive decay (T1∕2 = 5. 75 years), can be used as a proxy to constrain shelf fluxes of other trace elements, such as nutrients, iron, or rare earth elements. In this study, we perform inverse modeling of a global 228Ra dataset (including GEOSECS, TTO and GEOTRACES programs, and, for the first time, data from the Arctic and around the Kerguelen Islands) to compute the total 228Ra fluxes toward the ocean, using the ocean circulation obtained from the NEMO 3.6 model with a 2° resolution. We optimized the inverse calculation (source regions, cost function) and find a global estimate of the 228Ra fluxes of 8.01–8. 49 × 1023 atoms yr−1, more precise and around 20 % lower than previous estimates. The largest fluxes are in the western North Atlantic, the western Pacific and the Indian Ocean, with roughly two-thirds in the Indo-Pacific Basin. An estimate in the Arctic Ocean is provided for the first time (0.43–0.50 × 1023 atoms yr−1). Local misfits between model and data in the Arctic, the Gulf Stream and the Kuroshio regions could result from flaws of the ocean circulation in these regions (resolution, atmospheric forcing). As radium is enriched in groundwater, a large part of the 228Ra shelf sources comes from submarine groundwater discharge (SGD), a major but poorly known pathway for terrestrial mineral elements, including nutrients, to the ocean. In contrast to the 228Ra budget, the global estimate of SGD is rather unconstrained, between 1.3 and 14. 7 × 1013 m3 yr−1, due to high uncertainties on the other sources of 228Ra, especially diffusion from continental shelf sediments. Better precision on SGD cannot be reached by inverse modeling until a proper way to separate the contributions of SGD and diffusive release from sediments at a global scale is found This work is part of the first author’sPhD, ... Article in Journal/Newspaper Arctic Arctic Ocean Kerguelen Islands North Atlantic Digital.CSIC (Spanish National Research Council) Arctic Arctic Ocean Kerguelen Kerguelen Islands Pacific Indian Biogeosciences 14 13 3171 3189 |
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Open Polar |
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Digital.CSIC (Spanish National Research Council) |
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ftcsic |
language |
English |
description |
19 pages, 9 figures, 6 tables, supplement https://doi.org/10.5194/bg-14-3171-2017 Radium-228 (228Ra), an almost conservative trace isotope in the ocean, supplied from the continental shelves and removed by a known radioactive decay (T1∕2 = 5. 75 years), can be used as a proxy to constrain shelf fluxes of other trace elements, such as nutrients, iron, or rare earth elements. In this study, we perform inverse modeling of a global 228Ra dataset (including GEOSECS, TTO and GEOTRACES programs, and, for the first time, data from the Arctic and around the Kerguelen Islands) to compute the total 228Ra fluxes toward the ocean, using the ocean circulation obtained from the NEMO 3.6 model with a 2° resolution. We optimized the inverse calculation (source regions, cost function) and find a global estimate of the 228Ra fluxes of 8.01–8. 49 × 1023 atoms yr−1, more precise and around 20 % lower than previous estimates. The largest fluxes are in the western North Atlantic, the western Pacific and the Indian Ocean, with roughly two-thirds in the Indo-Pacific Basin. An estimate in the Arctic Ocean is provided for the first time (0.43–0.50 × 1023 atoms yr−1). Local misfits between model and data in the Arctic, the Gulf Stream and the Kuroshio regions could result from flaws of the ocean circulation in these regions (resolution, atmospheric forcing). As radium is enriched in groundwater, a large part of the 228Ra shelf sources comes from submarine groundwater discharge (SGD), a major but poorly known pathway for terrestrial mineral elements, including nutrients, to the ocean. In contrast to the 228Ra budget, the global estimate of SGD is rather unconstrained, between 1.3 and 14. 7 × 1013 m3 yr−1, due to high uncertainties on the other sources of 228Ra, especially diffusion from continental shelf sediments. Better precision on SGD cannot be reached by inverse modeling until a proper way to separate the contributions of SGD and diffusive release from sediments at a global scale is found This work is part of the first author’sPhD, ... |
format |
Article in Journal/Newspaper |
author |
Le Gland, Guillaume Mémery, L. Aumont, O. Resplandy, Laure |
spellingShingle |
Le Gland, Guillaume Mémery, L. Aumont, O. Resplandy, Laure Improving the inverse modeling of a trace isotope: how precisely can radium-228 fluxes toward the ocean and submarine groundwater discharge be estimated? |
author_facet |
Le Gland, Guillaume Mémery, L. Aumont, O. Resplandy, Laure |
author_sort |
Le Gland, Guillaume |
title |
Improving the inverse modeling of a trace isotope: how precisely can radium-228 fluxes toward the ocean and submarine groundwater discharge be estimated? |
title_short |
Improving the inverse modeling of a trace isotope: how precisely can radium-228 fluxes toward the ocean and submarine groundwater discharge be estimated? |
title_full |
Improving the inverse modeling of a trace isotope: how precisely can radium-228 fluxes toward the ocean and submarine groundwater discharge be estimated? |
title_fullStr |
Improving the inverse modeling of a trace isotope: how precisely can radium-228 fluxes toward the ocean and submarine groundwater discharge be estimated? |
title_full_unstemmed |
Improving the inverse modeling of a trace isotope: how precisely can radium-228 fluxes toward the ocean and submarine groundwater discharge be estimated? |
title_sort |
improving the inverse modeling of a trace isotope: how precisely can radium-228 fluxes toward the ocean and submarine groundwater discharge be estimated? |
publisher |
European Geosciences Union |
publishDate |
2017 |
url |
http://hdl.handle.net/10261/219715 https://doi.org/10.5194/bg-14-3171-2017 |
geographic |
Arctic Arctic Ocean Kerguelen Kerguelen Islands Pacific Indian |
geographic_facet |
Arctic Arctic Ocean Kerguelen Kerguelen Islands Pacific Indian |
genre |
Arctic Arctic Ocean Kerguelen Islands North Atlantic |
genre_facet |
Arctic Arctic Ocean Kerguelen Islands North Atlantic |
op_relation |
Publisher's version https://doi.org/10.5194/bg-14-3171-2017 No Biogeosciences 14: 3171-3189 (2017) 1726-4170 http://hdl.handle.net/10261/219715 doi:10.5194/bg-14-3171-2017 1726-4189 |
op_rights |
open |
op_doi |
https://doi.org/10.5194/bg-14-3171-2017 |
container_title |
Biogeosciences |
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14 |
container_issue |
13 |
container_start_page |
3171 |
op_container_end_page |
3189 |
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1790596703006490624 |