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Carbonate counter pump stimulated by natural iron fertilization in the Polar Frontal Zone

Carbonate counter pump stimulated by natural iron fertilization in the Polar Frontal Zone
Carbonate counter pump stimulated by natural iron fertilization in the Polar Frontal Zone
The production of organic carbon in the ocean’s surface and its subsequent downward export transfers carbon dioxide to the deep ocean. This CO2 drawdown is countered by the biological precipitation of carbonate, followed by sinking of particulate inorganic carbon, which is a source of carbon dioxide to the surface ocean, and hence the atmosphere over 100–1,000 year timescales1. The net transfer of CO2 to the deep ocean is therefore dependent on the relative amount of organic and inorganic carbon in sinking particles2. In the Southern Ocean, iron fertilization has been shown to increase the export of organic carbon3, 4, 5, but it is unclear to what degree this effect is compensated by the export of inorganic carbon. Here we assess the composition of sinking particles collected from sediment traps located in the Polar Frontal Zone of the Southern Ocean. We find that in high-nutrient, low-chlorophyll regions that are characterized by naturally high iron concentrations, fluxes of both organic and inorganic carbon are higher than in regions with no iron fertilization. However, the excess flux of inorganic carbon is greater than that of organic carbon. We estimate that the production and flux of carbonate in naturally iron-fertilized waters reduces the overall amount of CO2 transferred to the deep ocean by 6–32%, compared to 1–4% at the non-fertilized site. We suggest that an increased export of organic carbon, stimulated by iron availability in the glacial sub-Antarctic oceans, may have been accompanied by a strengthened carbonate counter pump.
1752-0894
885-889
Salter, Ian
af9ab647-8d56-4420-b84b-4615582b0289
Schiebel, Ralf
5c48accb-ee14-471a-801f-4267d8e4b2e1
Ziveri, Patrizia
7c2b4b39-88dd-4765-abac-40405843d220
Movellan, Aurore
a35c7050-2900-47d5-af23-aab402963a3b
Lampitt, Richard
dfc3785c-fc7d-41fa-89ee-d0c6e27503ad
Wolff, George A.
6b29d886-06f9-4405-8fab-33cfb436acaa
Salter, Ian
af9ab647-8d56-4420-b84b-4615582b0289
Schiebel, Ralf
5c48accb-ee14-471a-801f-4267d8e4b2e1
Ziveri, Patrizia
7c2b4b39-88dd-4765-abac-40405843d220
Movellan, Aurore
a35c7050-2900-47d5-af23-aab402963a3b
Lampitt, Richard
dfc3785c-fc7d-41fa-89ee-d0c6e27503ad
Wolff, George A.
6b29d886-06f9-4405-8fab-33cfb436acaa

Salter, Ian, Schiebel, Ralf, Ziveri, Patrizia, Movellan, Aurore, Lampitt, Richard and Wolff, George A. (2014) Carbonate counter pump stimulated by natural iron fertilization in the Polar Frontal Zone. Nature Geoscience, 7, 885-889. (doi:10.1038/ngeo2285).

Record type: Article

Abstract

The production of organic carbon in the ocean’s surface and its subsequent downward export transfers carbon dioxide to the deep ocean. This CO2 drawdown is countered by the biological precipitation of carbonate, followed by sinking of particulate inorganic carbon, which is a source of carbon dioxide to the surface ocean, and hence the atmosphere over 100–1,000 year timescales1. The net transfer of CO2 to the deep ocean is therefore dependent on the relative amount of organic and inorganic carbon in sinking particles2. In the Southern Ocean, iron fertilization has been shown to increase the export of organic carbon3, 4, 5, but it is unclear to what degree this effect is compensated by the export of inorganic carbon. Here we assess the composition of sinking particles collected from sediment traps located in the Polar Frontal Zone of the Southern Ocean. We find that in high-nutrient, low-chlorophyll regions that are characterized by naturally high iron concentrations, fluxes of both organic and inorganic carbon are higher than in regions with no iron fertilization. However, the excess flux of inorganic carbon is greater than that of organic carbon. We estimate that the production and flux of carbonate in naturally iron-fertilized waters reduces the overall amount of CO2 transferred to the deep ocean by 6–32%, compared to 1–4% at the non-fertilized site. We suggest that an increased export of organic carbon, stimulated by iron availability in the glacial sub-Antarctic oceans, may have been accompanied by a strengthened carbonate counter pump.

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More information

Published date: November 2014
Organisations: Marine Biogeochemistry

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Local EPrints ID: 372204
URI: http://eprints.soton.ac.uk/id/eprint/372204
ISSN: 1752-0894
PURE UUID: b1ca9436-52f4-4194-9e28-410cfeb76b51

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Date deposited: 27 Nov 2014 11:53
Last modified: 27 Apr 2022 04:12

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Contributors

Author: Ian Salter
Author: Ralf Schiebel
Author: Patrizia Ziveri
Author: Aurore Movellan
Author: Richard Lampitt
Author: George A. Wolff

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