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

The ocean contributes to regulating atmospheric CO2 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 betwe...

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Bibliographic Details
Published in:Geophysical Research Letters
Main Authors: Le Moigne, Frederic A. C., Henson, Stephanie A., Cavan, Emma, Georges, Clément, Pabortsava, Katsiaryna, Achterberg, Eric P., Ceballos-Romero, Elena, Zubkov, Mike, Sanders, Richard J.
Format: Article in Journal/Newspaper
Language:English
Published: AGU (American Geophysical Union) 2016
Subjects:
Southern Ocean
Online Access:https://oceanrep.geomar.de/id/eprint/32903/
https://oceanrep.geomar.de/id/eprint/32903/7/grl54298%281%29.pdf
https://doi.org/10.1002/2016GL068480
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Summary:The ocean contributes to regulating atmospheric CO2 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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