Processes controlling the Si-isotopic composition in the Southern Ocean and application for paleoceanography
Southern Ocean biogeochemical processes have an impact on global marine primary production and global elemental cycling, e.g. by likely controlling glacial-interglacial pCO(2) variation. In this context, the natural silicon isotopic composition (delta Si-30) of sedimentary biogenic silica has been u...
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ftarchimer:oai:archimer.ifremer.fr:33769 2023-05-15T16:55:52+02:00 Processes controlling the Si-isotopic composition in the Southern Ocean and application for paleoceanography Fripiat, F. Cavagna, A. -j. Dehairs, F. De Brauwere, A. Andre, L. Cardinal, D. 2012 application/pdf https://archimer.ifremer.fr/doc/00226/33769/32565.pdf https://doi.org/10.5194/bg-9-2443-2012 https://archimer.ifremer.fr/doc/00226/33769/ eng eng Copernicus Gesellschaft Mbh https://archimer.ifremer.fr/doc/00226/33769/32565.pdf doi:10.5194/bg-9-2443-2012 https://archimer.ifremer.fr/doc/00226/33769/ Author(s) 2012. This work is distributed under the Creative Commons Attribution 3.0 License. info:eu-repo/semantics/openAccess restricted use CC-BY Biogeosciences (1726-4170) (Copernicus Gesellschaft Mbh), 2012 , Vol. 9 , N. 7 , P. 2443-2457 text Publication info:eu-repo/semantics/article 2012 ftarchimer https://doi.org/10.5194/bg-9-2443-2012 2021-09-23T20:25:10Z Southern Ocean biogeochemical processes have an impact on global marine primary production and global elemental cycling, e.g. by likely controlling glacial-interglacial pCO(2) variation. In this context, the natural silicon isotopic composition (delta Si-30) of sedimentary biogenic silica has been used to reconstruct past Si-consumption:supply ratios in the surface waters. We present a new dataset in the Southern Ocean from a IPY-GEOTRACES transect (Bonus-GoodHope) which includes for the first time summer delta Si-30 signatures of suspended biogenic silica (i) for the whole water column at three stations and (ii) in the mixed layer at seven stations from the subtropical zone up to the Weddell Gyre. In general, the isotopic composition of biogenic opal exported to depth was comparable to the opal leaving the mixed layer and did not seem to be affected by any diagenetic processes during settling, even if an effect of biogenic silica dissolution cannot be ruled out in the northern part of the Weddell Gyre. We develop a mechanistic understanding of the processes involved in the modern Si-isotopic balance, by implementing a mixed layer model. We observe that the accumulated biogenic silica (sensu Rayleigh distillation) should satisfactorily describe the delta Si-30 composition of biogenic silica exported out of the mixed layer, within the limit of the current analytical precision on the delta Si-30. The failures of previous models (Rayleigh and steady state) become apparent especially at the end of the productive period in the mixed layer, when biogenic silica production and export are low. This results from (1) a higher biogenic silica dissolution:production ratio imposing a lower net fractionation factor and (2) a higher Si-supply:Si-uptake ratio supplying light Si-isotopes into the mixed layer. The latter effect is especially expressed when the summer mixed layer becomes strongly Si-depleted, together with a large vertical silicic acid gradient, e.g. in the Polar Front Zone and at the Polar Front. Article in Journal/Newspaper IPY Southern Ocean Archimer (Archive Institutionnelle de l'Ifremer - Institut français de recherche pour l'exploitation de la mer) Southern Ocean Weddell Biogeosciences 9 7 2443 2457 |
institution |
Open Polar |
collection |
Archimer (Archive Institutionnelle de l'Ifremer - Institut français de recherche pour l'exploitation de la mer) |
op_collection_id |
ftarchimer |
language |
English |
description |
Southern Ocean biogeochemical processes have an impact on global marine primary production and global elemental cycling, e.g. by likely controlling glacial-interglacial pCO(2) variation. In this context, the natural silicon isotopic composition (delta Si-30) of sedimentary biogenic silica has been used to reconstruct past Si-consumption:supply ratios in the surface waters. We present a new dataset in the Southern Ocean from a IPY-GEOTRACES transect (Bonus-GoodHope) which includes for the first time summer delta Si-30 signatures of suspended biogenic silica (i) for the whole water column at three stations and (ii) in the mixed layer at seven stations from the subtropical zone up to the Weddell Gyre. In general, the isotopic composition of biogenic opal exported to depth was comparable to the opal leaving the mixed layer and did not seem to be affected by any diagenetic processes during settling, even if an effect of biogenic silica dissolution cannot be ruled out in the northern part of the Weddell Gyre. We develop a mechanistic understanding of the processes involved in the modern Si-isotopic balance, by implementing a mixed layer model. We observe that the accumulated biogenic silica (sensu Rayleigh distillation) should satisfactorily describe the delta Si-30 composition of biogenic silica exported out of the mixed layer, within the limit of the current analytical precision on the delta Si-30. The failures of previous models (Rayleigh and steady state) become apparent especially at the end of the productive period in the mixed layer, when biogenic silica production and export are low. This results from (1) a higher biogenic silica dissolution:production ratio imposing a lower net fractionation factor and (2) a higher Si-supply:Si-uptake ratio supplying light Si-isotopes into the mixed layer. The latter effect is especially expressed when the summer mixed layer becomes strongly Si-depleted, together with a large vertical silicic acid gradient, e.g. in the Polar Front Zone and at the Polar Front. |
format |
Article in Journal/Newspaper |
author |
Fripiat, F. Cavagna, A. -j. Dehairs, F. De Brauwere, A. Andre, L. Cardinal, D. |
spellingShingle |
Fripiat, F. Cavagna, A. -j. Dehairs, F. De Brauwere, A. Andre, L. Cardinal, D. Processes controlling the Si-isotopic composition in the Southern Ocean and application for paleoceanography |
author_facet |
Fripiat, F. Cavagna, A. -j. Dehairs, F. De Brauwere, A. Andre, L. Cardinal, D. |
author_sort |
Fripiat, F. |
title |
Processes controlling the Si-isotopic composition in the Southern Ocean and application for paleoceanography |
title_short |
Processes controlling the Si-isotopic composition in the Southern Ocean and application for paleoceanography |
title_full |
Processes controlling the Si-isotopic composition in the Southern Ocean and application for paleoceanography |
title_fullStr |
Processes controlling the Si-isotopic composition in the Southern Ocean and application for paleoceanography |
title_full_unstemmed |
Processes controlling the Si-isotopic composition in the Southern Ocean and application for paleoceanography |
title_sort |
processes controlling the si-isotopic composition in the southern ocean and application for paleoceanography |
publisher |
Copernicus Gesellschaft Mbh |
publishDate |
2012 |
url |
https://archimer.ifremer.fr/doc/00226/33769/32565.pdf https://doi.org/10.5194/bg-9-2443-2012 https://archimer.ifremer.fr/doc/00226/33769/ |
geographic |
Southern Ocean Weddell |
geographic_facet |
Southern Ocean Weddell |
genre |
IPY Southern Ocean |
genre_facet |
IPY Southern Ocean |
op_source |
Biogeosciences (1726-4170) (Copernicus Gesellschaft Mbh), 2012 , Vol. 9 , N. 7 , P. 2443-2457 |
op_relation |
https://archimer.ifremer.fr/doc/00226/33769/32565.pdf doi:10.5194/bg-9-2443-2012 https://archimer.ifremer.fr/doc/00226/33769/ |
op_rights |
Author(s) 2012. This work is distributed under the Creative Commons Attribution 3.0 License. info:eu-repo/semantics/openAccess restricted use |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.5194/bg-9-2443-2012 |
container_title |
Biogeosciences |
container_volume |
9 |
container_issue |
7 |
container_start_page |
2443 |
op_container_end_page |
2457 |
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1766046915057680384 |