Exploring interacting influences on the silicon isotopic composition of the surface ocean: a case study from the Kerguelen Plateau
This study presents six new water column profiles of the silicon isotopic composition (δ 30 Si) of dissolved silicon (DSi) from the Atlantic and Indian sectors of the Southern Ocean and a variable depth box model of silica cycling in the mixed layer that was constructed to illuminate the evolution o...
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2014
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ftdoajarticles:oai:doaj.org/article:80059bdd2e98489587a5b2033e7a3f59 2023-05-15T18:26:00+02:00 Exploring interacting influences on the silicon isotopic composition of the surface ocean: a case study from the Kerguelen Plateau N. Coffineau C. L. De La Rocha P. Pondaven 2014-03-01T00:00:00Z https://doi.org/10.5194/bg-11-1371-2014 https://doaj.org/article/80059bdd2e98489587a5b2033e7a3f59 EN eng Copernicus Publications http://www.biogeosciences.net/11/1371/2014/bg-11-1371-2014.pdf https://doaj.org/toc/1726-4170 https://doaj.org/toc/1726-4189 1726-4170 1726-4189 doi:10.5194/bg-11-1371-2014 https://doaj.org/article/80059bdd2e98489587a5b2033e7a3f59 Biogeosciences, Vol 11, Iss 5, Pp 1371-1391 (2014) Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 article 2014 ftdoajarticles https://doi.org/10.5194/bg-11-1371-2014 2022-12-31T00:36:22Z This study presents six new water column profiles of the silicon isotopic composition (δ 30 Si) of dissolved silicon (DSi) from the Atlantic and Indian sectors of the Southern Ocean and a variable depth box model of silica cycling in the mixed layer that was constructed to illuminate the evolution of surface ocean δ 30 Si over the full course of a year. In keeping with previous observations, δ 30 Si values ranged from +1.9 to +2.4‰ in the mixed layer (ML), +1.2 to +1.7‰ in Winter Water (WW), and +0.9 to +1.4‰ in Circumpolar Deep Water (CDW). These data also confirmed the occurrence of diminished values for ML δ 30 Si at low DSi concentrations in early austral autumn on the Kerguelen Plateau. The box model was used to investigate whether these low, post-growing season values of δ 30 Si were related to input of DSi to the ML from basalt weathering, biogenic silica dissolution (with or without isotopic fractionation), the onset of winter mixing, or some combination of the three. Basalt weathering and fractionation during biogenic silica dissolution could both lower ML δ 30 Si below what would be expected from the extent of biological uptake of DSi. However, the key driver of the early autumn decrease in δ 30 Si appears to be the switch from bloom growth (with net removal of DSi and net accumulation of biogenic silica (BSi) biomass) to steady state growth (when slow but continuing production of BSi prevented significant net increase in DSi concentrations with diffusive input of DSi from WW but not decrease in ML δ 30 Si towards WW values). Model results also indicated that fractionation during dissolution has only a negligible effect on the δ 30 Si of BSi exported throughout the course of the year. However, seasonal changes in export efficiency (e.g. favouring the export of bloom BSi versus the export of BSi produced during other times of the year) should strongly influence the δ 30 Si of BSi accumulating in marine sediments. Finally, the choice for the parameterisation of the mixing between the ML and the WW in ... Article in Journal/Newspaper Southern Ocean Directory of Open Access Journals: DOAJ Articles Southern Ocean Austral Kerguelen Indian Biogeosciences 11 5 1371 1391 |
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Open Polar |
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Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 |
spellingShingle |
Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 N. Coffineau C. L. De La Rocha P. Pondaven Exploring interacting influences on the silicon isotopic composition of the surface ocean: a case study from the Kerguelen Plateau |
topic_facet |
Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 |
description |
This study presents six new water column profiles of the silicon isotopic composition (δ 30 Si) of dissolved silicon (DSi) from the Atlantic and Indian sectors of the Southern Ocean and a variable depth box model of silica cycling in the mixed layer that was constructed to illuminate the evolution of surface ocean δ 30 Si over the full course of a year. In keeping with previous observations, δ 30 Si values ranged from +1.9 to +2.4‰ in the mixed layer (ML), +1.2 to +1.7‰ in Winter Water (WW), and +0.9 to +1.4‰ in Circumpolar Deep Water (CDW). These data also confirmed the occurrence of diminished values for ML δ 30 Si at low DSi concentrations in early austral autumn on the Kerguelen Plateau. The box model was used to investigate whether these low, post-growing season values of δ 30 Si were related to input of DSi to the ML from basalt weathering, biogenic silica dissolution (with or without isotopic fractionation), the onset of winter mixing, or some combination of the three. Basalt weathering and fractionation during biogenic silica dissolution could both lower ML δ 30 Si below what would be expected from the extent of biological uptake of DSi. However, the key driver of the early autumn decrease in δ 30 Si appears to be the switch from bloom growth (with net removal of DSi and net accumulation of biogenic silica (BSi) biomass) to steady state growth (when slow but continuing production of BSi prevented significant net increase in DSi concentrations with diffusive input of DSi from WW but not decrease in ML δ 30 Si towards WW values). Model results also indicated that fractionation during dissolution has only a negligible effect on the δ 30 Si of BSi exported throughout the course of the year. However, seasonal changes in export efficiency (e.g. favouring the export of bloom BSi versus the export of BSi produced during other times of the year) should strongly influence the δ 30 Si of BSi accumulating in marine sediments. Finally, the choice for the parameterisation of the mixing between the ML and the WW in ... |
format |
Article in Journal/Newspaper |
author |
N. Coffineau C. L. De La Rocha P. Pondaven |
author_facet |
N. Coffineau C. L. De La Rocha P. Pondaven |
author_sort |
N. Coffineau |
title |
Exploring interacting influences on the silicon isotopic composition of the surface ocean: a case study from the Kerguelen Plateau |
title_short |
Exploring interacting influences on the silicon isotopic composition of the surface ocean: a case study from the Kerguelen Plateau |
title_full |
Exploring interacting influences on the silicon isotopic composition of the surface ocean: a case study from the Kerguelen Plateau |
title_fullStr |
Exploring interacting influences on the silicon isotopic composition of the surface ocean: a case study from the Kerguelen Plateau |
title_full_unstemmed |
Exploring interacting influences on the silicon isotopic composition of the surface ocean: a case study from the Kerguelen Plateau |
title_sort |
exploring interacting influences on the silicon isotopic composition of the surface ocean: a case study from the kerguelen plateau |
publisher |
Copernicus Publications |
publishDate |
2014 |
url |
https://doi.org/10.5194/bg-11-1371-2014 https://doaj.org/article/80059bdd2e98489587a5b2033e7a3f59 |
geographic |
Southern Ocean Austral Kerguelen Indian |
geographic_facet |
Southern Ocean Austral Kerguelen Indian |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_source |
Biogeosciences, Vol 11, Iss 5, Pp 1371-1391 (2014) |
op_relation |
http://www.biogeosciences.net/11/1371/2014/bg-11-1371-2014.pdf https://doaj.org/toc/1726-4170 https://doaj.org/toc/1726-4189 1726-4170 1726-4189 doi:10.5194/bg-11-1371-2014 https://doaj.org/article/80059bdd2e98489587a5b2033e7a3f59 |
op_doi |
https://doi.org/10.5194/bg-11-1371-2014 |
container_title |
Biogeosciences |
container_volume |
11 |
container_issue |
5 |
container_start_page |
1371 |
op_container_end_page |
1391 |
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1766207776235716608 |