What causes the inverse relationship between primary production and export efficiency in the Southern Ocean?

International audience The ocean contributes to regulating atmospheric CO 2 levels, partly via variability in the fraction of primary production (PP) which is exported out of the surface layer (i.e., the e ratio). Southern Ocean studies have found that contrary to global-scale analyses, an inverse r...

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Bibliographic Details
Published in:Geophysical Research Letters
Main Authors: Le Moigne, Frédéric A.C., Henson, Stephanie, Cavan, Emma, Georges, Clément, Pabortsava, Katsiaryna, Achterberg, Eric, Ceballos-Romero, Elena, Zubkov, Mike, Sanders, Richard
Other Authors: National Oceanography Centre Southampton (NOC), University of Southampton, Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 (LOG), Institut national des sciences de l'Univers (INSU - CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD France-Nord ), Helmholtz Centre for Ocean Research Kiel (GEOMAR)
Format: Article in Journal/Newspaper
Language:English
Published: HAL CCSD 2016
Subjects:
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean
Atmosphere
Southern Ocean
Online Access:https://hal.archives-ouvertes.fr/hal-02345498
https://hal.archives-ouvertes.fr/hal-02345498/document
https://hal.archives-ouvertes.fr/hal-02345498/file/2016GL068480.pdf
https://doi.org/10.1002/2016GL068480
Description
Summary:International audience The ocean contributes to regulating atmospheric CO 2 levels, partly via variability in the fraction of primary production (PP) which is exported out of the surface layer (i.e., the e ratio). Southern Ocean studies have found that contrary to global-scale analyses, an inverse relationship exists between e ratio and PP. This relationship remains unexplained, with potential hypotheses being (i) large export of dissolved organic carbon (DOC) in high PP areas, (ii) strong surface microbial recycling in high PP regions, and/or (iii) grazing-mediated export that varies inversely with PP. We find that the export of DOC has a limited influence in setting the negative e ratio/PP relationship. However, we observed that at sites with low PP and high e ratios, zooplankton-mediated export is large and surface microbial abundance low suggesting that both are important drivers of the magnitude of the e ratio in the Southern Ocean.

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