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Slow Sinking Particulate Organic Carbon in the Atlantic Ocean: magnitude, flux and potential controls

Slow Sinking Particulate Organic Carbon in the Atlantic Ocean: magnitude, flux and potential controls
Slow Sinking Particulate Organic Carbon in the Atlantic Ocean: magnitude, flux and potential controls
The remineralization depth of particulate organic carbon (POC) fluxes exported from the surface ocean exert a major control over atmospheric CO₂ levels. According to a long held paradigm most of the POC exported to depth is associated with large particles. However, recent lines of evidence suggest that slow sinking POC (SSPOC) may be an important contributor to this flux. Here we assess the circumstances under which this occurs. Our study uses samples collected using the Marine Snow Catcher throughout the Atlantic Ocean, from high latitudes to mid latitudes. We find median SSPOC concentrations of 5.5 μg L-1, 13 times smaller than suspended POC concentrations and 75 times higher than median fast sinking POC (FSPOC) concentrations (0.07 μg L-1). Export fluxes of SSPOC generally exceed FSPOC flux, with the exception being during a spring bloom sampled in the Southern Ocean. In the Southern Ocean SSPOC fluxes often increase with depth relative to FSPOC flux, likely due to midwater fragmentation of FSPOC, a process which may contribute to shallow mineralization of POC and hence to reduced carbon storage. Biogeochemical models do not generally reproduce this behaviour, meaning that they likely overestimate long term ocean carbon storage.
0886-6236
1051–1065
Baker, Chelsey A.
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Henson, Stephanie A.
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Cavan, Emma L.
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Giering, Sarah L.C.
e9b75287-e35e-414a-a5f2-cef9f2ab2efd
Yool, Andrew
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Gehlen, Marion
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Belcher, Anna
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Riley, Jennifer S.
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Smith, Helen E. K.
e9ebdc59-6964-49b5-a2cd-b76d58ab77e1
Sanders, Richard
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Baker, Chelsey A.
66c098dd-5e13-4b03-a7e7-35122aef8f26
Henson, Stephanie A.
d6532e17-a65b-4d7b-9ee3-755ecb565c19
Cavan, Emma L.
aca6bc0e-f2ba-4378-8be6-4da7e1e9da31
Giering, Sarah L.C.
e9b75287-e35e-414a-a5f2-cef9f2ab2efd
Yool, Andrew
882aeb0d-dda0-405e-844c-65b68cce5017
Gehlen, Marion
e4883d9b-b726-46b9-abcd-c2915e5cee51
Belcher, Anna
1808c30a-c05b-410e-85c1-4b01c1e69d80
Riley, Jennifer S.
4cf9f8c5-5c07-466b-83de-4088f97d498c
Smith, Helen E. K.
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Sanders, Richard
02c163c1-8f5e-49ad-857c-d28f7da66c65

Baker, Chelsey A., Henson, Stephanie A., Cavan, Emma L., Giering, Sarah L.C., Yool, Andrew, Gehlen, Marion, Belcher, Anna, Riley, Jennifer S., Smith, Helen E. K. and Sanders, Richard (2017) Slow Sinking Particulate Organic Carbon in the Atlantic Ocean: magnitude, flux and potential controls. Global Biogeochemical Cycles, 31 (7), 1051–1065. (doi:10.1002/2017GB005638).

Record type: Article

Abstract

The remineralization depth of particulate organic carbon (POC) fluxes exported from the surface ocean exert a major control over atmospheric CO₂ levels. According to a long held paradigm most of the POC exported to depth is associated with large particles. However, recent lines of evidence suggest that slow sinking POC (SSPOC) may be an important contributor to this flux. Here we assess the circumstances under which this occurs. Our study uses samples collected using the Marine Snow Catcher throughout the Atlantic Ocean, from high latitudes to mid latitudes. We find median SSPOC concentrations of 5.5 μg L-1, 13 times smaller than suspended POC concentrations and 75 times higher than median fast sinking POC (FSPOC) concentrations (0.07 μg L-1). Export fluxes of SSPOC generally exceed FSPOC flux, with the exception being during a spring bloom sampled in the Southern Ocean. In the Southern Ocean SSPOC fluxes often increase with depth relative to FSPOC flux, likely due to midwater fragmentation of FSPOC, a process which may contribute to shallow mineralization of POC and hence to reduced carbon storage. Biogeochemical models do not generally reproduce this behaviour, meaning that they likely overestimate long term ocean carbon storage.

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Accepted/In Press date: 11 June 2017
e-pub ahead of print date: 11 July 2017
Organisations: Ocean and Earth Science, Marine Biogeochemistry, National Oceanography Centre

Identifiers

Local EPrints ID: 411978
URI: https://eprints.soton.ac.uk/id/eprint/411978
ISSN: 0886-6236
PURE UUID: 2f19444b-ecf9-4e89-b501-901bd6f1be66
ORCID for Chelsey A. Baker: ORCID iD orcid.org/0000-0002-0840-2333

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Date deposited: 04 Jul 2017 16:31
Last modified: 03 Dec 2019 01:29

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