Potentially bioavailable iron delivery by iceberg-hosted sediments and atmospheric dust to the polar oceans

Iceberg-hosted sediments and atmospheric dust transport potentially bioavailable iron to the Arctic and Southern oceans as ferrihydrite. Ferrihydrite is nanoparticulate and more soluble, as well as potentially more bioavailable, than other iron (oxyhydr)oxide minerals (lepidocrocite, goethite, and h...

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Bibliographic Details
Published in:Biogeosciences
Main Authors: Raiswell, Robert, Hawkings, Jon R., Benning, Liane G., Baker, Alex R., Death, Ros, Albani, Samuel, Mahowald, Natalie, Krom, Michael D., Poulton, Simon W., Wadham, Jemma, Tranter, Martyn
Other Authors: Raiswell, R, Hawkings, J, Benning, L, Baker, A, Death, R, Albani, S, Mahowald, N, Krom, M, Poulton, S, Wadham, J, Tranter, M
Format: Article in Journal/Newspaper
Language:English
Published: Copernicus GmbH 2016
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Online Access:http://hdl.handle.net/10281/217652
https://doi.org/10.5194/bg-13-3887-2016
http://www.biogeosciences.net/volumes_and_issues.html
Description
Summary:Iceberg-hosted sediments and atmospheric dust transport potentially bioavailable iron to the Arctic and Southern oceans as ferrihydrite. Ferrihydrite is nanoparticulate and more soluble, as well as potentially more bioavailable, than other iron (oxyhydr)oxide minerals (lepidocrocite, goethite, and hematite). A suite of more than 50 iceberg-hosted sediments contain a mean content of 0.076 wt % Fe as ferrihydrite, which produces iceberg-hosted Fe fluxes ranging from 0.7 to 5.5 and 3.2 to 25 Gmoles yr-1 to the Arctic and Southern oceans respectively. Atmospheric dust (with little or no combustion products) contains a mean ferrihydrite Fe content of 0.038 wt % (corresponding to a fractional solubility of ∼1 %) and delivers much smaller Fe fluxes (0.02-0.07 Gmoles yr-1 to the Arctic Ocean and 0.0-0.02 Gmoles yr-1 to the Southern Ocean). New dust flux data show that most atmospheric dust is delivered to sea ice where exposure to melting/re-freezing cycles may enhance fractional solubility, and thus fluxes, by a factor of approximately 2.5. Improved estimates for these particulate sources require additional data for the iceberg losses during fjord transit, the sediment content of icebergs, and samples of atmospheric dust delivered to the polar regions.