Highly bioavailable dust-borne iron delivered to the Southern Ocean during glacial periods

Dust-borne iron fertilization of Southern Ocean phytoplankton contributes to lower glacial atmospheric CO2. Previous studies evaluating the impact of dust on climate estimate bioavailable iron using total iron fluxes in sediment cores. Thus, all iron is considered equally bioavailable over geologic...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences
Main Authors: Shoenfelt, Elizabeth M., Winckler, Gisela, Lamy, Frank, Anderson, Robert F., Bostick, Benjamin C.
Format: Text
Language:English
Published: National Academy of Sciences 2018
Subjects:
Physical Sciences
Southern Ocean
Online Access:http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6217405/
http://www.ncbi.nlm.nih.gov/pubmed/30322933
https://doi.org/10.1073/pnas.1809755115
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Summary:Dust-borne iron fertilization of Southern Ocean phytoplankton contributes to lower glacial atmospheric CO2. Previous studies evaluating the impact of dust on climate estimate bioavailable iron using total iron fluxes in sediment cores. Thus, all iron is considered equally bioavailable over geologic time, despite evidence that glaciers mobilize highly bioavailable iron from bedrock, which winds can deliver to the Southern Ocean. Here we reconstruct dust-borne iron speciation over the last glacial cycle, showing that highly bioavailable iron(II) silicate minerals are a greater fraction of total iron reaching the Southern Ocean during glacial periods. The abundance of iron(II) silicates likely controls the bioavailable iron supply to the Southern Ocean and contributes to the previously observed increase in glacial productivity and CO2 drawdown.

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