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High‐frequency variability of small‐particle carbon export flux in the Northeast Atlantic

High‐frequency variability of small‐particle carbon export flux in the Northeast Atlantic
High‐frequency variability of small‐particle carbon export flux in the Northeast Atlantic
The biological carbon pump exports carbon fixed by photosynthesis out of the surface ocean and transfers it to the deep, mostly in the form of sinking particles. Despite the importance of the pump in regulating the air‐sea CO2 balance, the magnitude of global carbon export remains unclear, as do its controlling mechanisms. A possible sinking flux of carbon to the mesopelagic zone may be via the mixed‐layer pump: a seasonal net detrainment of particulate organic carbon (POC)‐rich surface waters, caused by sequential deepening and shoaling of the mixed layer. In this study, we present a full year of daily small‐particle POC concentrations derived from glider optical backscatter data, to study export variability at the Porcupine Abyssal Plain (PAP) sustained observatory in the Northeast Atlantic. We observe a strong seasonality in small‐particle transfer efficiency, with a maximum in winter and early spring. By calculating daily POC export driven by mixed‐layer variations, we find that the mixed‐layer pump supplies an annual flux of at least 3.0 ± 0.9 g POC·m−2·year−1 to the mesopelagic zone, contributing between 5% and 25% of the total annual export flux and likely contributing to closing a gap in the mesopelagic carbon budget found by other studies. These are, to our best knowledge, the first high‐frequency observations of export variability over the course of a full year. Our results support the deployment of bio‐optical sensors on gliders to improve our understanding of the ocean carbon cycle on temporal scales from daily to annual.
0886-6236
1803-1814
Bol, Roséanne
2df7982f-34bb-4a2b-aab1-b4af09e3bfbb
Henson, Stephanie, Anne
d6532e17-a65b-4d7b-9ee3-755ecb565c19
Rumyantseva, Anna
44ccfbcf-2dc4-48ea-86f3-85eb511acac6
Briggs, Nathan
a53aa80d-785a-4ace-99d3-72fa05e94471
Bol, Roséanne
2df7982f-34bb-4a2b-aab1-b4af09e3bfbb
Henson, Stephanie, Anne
d6532e17-a65b-4d7b-9ee3-755ecb565c19
Rumyantseva, Anna
44ccfbcf-2dc4-48ea-86f3-85eb511acac6
Briggs, Nathan
a53aa80d-785a-4ace-99d3-72fa05e94471

Bol, Roséanne, Henson, Stephanie, Anne, Rumyantseva, Anna and Briggs, Nathan (2018) High‐frequency variability of small‐particle carbon export flux in the Northeast Atlantic. Global Biogeochemical Cycles, 1803-1814. (doi:10.1029/2018GB005963).

Record type: Article

Abstract

The biological carbon pump exports carbon fixed by photosynthesis out of the surface ocean and transfers it to the deep, mostly in the form of sinking particles. Despite the importance of the pump in regulating the air‐sea CO2 balance, the magnitude of global carbon export remains unclear, as do its controlling mechanisms. A possible sinking flux of carbon to the mesopelagic zone may be via the mixed‐layer pump: a seasonal net detrainment of particulate organic carbon (POC)‐rich surface waters, caused by sequential deepening and shoaling of the mixed layer. In this study, we present a full year of daily small‐particle POC concentrations derived from glider optical backscatter data, to study export variability at the Porcupine Abyssal Plain (PAP) sustained observatory in the Northeast Atlantic. We observe a strong seasonality in small‐particle transfer efficiency, with a maximum in winter and early spring. By calculating daily POC export driven by mixed‐layer variations, we find that the mixed‐layer pump supplies an annual flux of at least 3.0 ± 0.9 g POC·m−2·year−1 to the mesopelagic zone, contributing between 5% and 25% of the total annual export flux and likely contributing to closing a gap in the mesopelagic carbon budget found by other studies. These are, to our best knowledge, the first high‐frequency observations of export variability over the course of a full year. Our results support the deployment of bio‐optical sensors on gliders to improve our understanding of the ocean carbon cycle on temporal scales from daily to annual.

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Bol et al 2018 Global Biogeochemical Cycles - Version of Record
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Accepted/In Press date: 4 December 2018
Published date: 18 December 2018

Identifiers

Local EPrints ID: 427651
URI: http://eprints.soton.ac.uk/id/eprint/427651
ISSN: 0886-6236
PURE UUID: 58d20575-677a-4559-b8f5-d9e1a937019e

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Date deposited: 25 Jan 2019 17:30
Last modified: 16 Dec 2019 17:45

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