Carbon sequestration in the deep Atlantic enhanced by Saharan dust

Pabortsava, Katsiaryna; Lampitt, Richard; Benson, Jeff; Crowe, Chris; McLachlan, Robert; Le Moigne, Frederic A.C.; Moore, C. Mark; Pebody, Corinne; Provost, Paul; Rees, Andrew; Tilstone, Gavin; Woodword, E. Malcolm. 2017 Carbon sequestration in the deep Atlantic enhanced by Saharan dust. Nature Geoscience, 10 (3). 189-194. 10.1038/ngeo2899

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Text © 2017 Nature Publishing Group This is the author’s version of a work that was accepted for publication in Nature. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version will be published in Nature doi:10.1038/ngeo2899 Pabortsava_et_al_2017.pdf - Accepted Version Download (1MB) | Preview

Abstract/Summary

Enhanced atmospheric input of dust-borne nutrients and minerals to the remote surface ocean can potentially increase carbon uptake and sequestration at depth. Nutrients can enhance primary productivity, and mineral particles act as ballast, increasing sinking rates of particulate organic matter. Here we present a two-year time series of sediment trap observations of particulate organic carbon flux to 3,000 m depth, measured directly in two locations: the dust-rich central North Atlantic gyre and the dust-poor South Atlantic gyre. We find that carbon fluxes are twice as high and a higher proportion of primary production is exported to depth in the dust-rich North Atlantic gyre. Low stable nitrogen isotope ratios suggest that high fluxes result from the stimulation of nitrogen fixation and productivity following the deposition of dust-borne nutrients. Sediment traps in the northern gyre also collected intact colonies of nitrogen-fixing Trichodesmium species. Whereas ballast in the southern gyre is predominantly biogenic, dust-derived mineral particles constitute the dominant ballast element during the enhanced carbon fluxes in the northern gyre. We conclude that dust deposition increases carbon sequestration in the North Atlantic gyre through the fertilization of the nitrogen-fixing community in surface waters and mineral ballasting of sinking particles.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1038/ngeo2899
ISSN:	1752-0894
Date made live:	28 Feb 2017 16:14 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/516336

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