Abstract
The micronutrient iron is thought to limit primary productivity in large regions of the global ocean1. Ice sheets and glaciers have been shown to deliver bioavailable iron to the coastal and open ocean in the form of sediment released from the base of icebergs2,3 and glacially derived dust4. More direct measurements from glacial runoff are limited, but iron concentrations are thought to be in the nanomolar range5. Here we present measurements of dissolved and particulate iron concentrations in glacial meltwater from the southwest margin of the Greenland ice sheet. We report micromolar concentrations of dissolved and particulate iron. Particulate iron concentrations were on average an order of magnitude higher than those of dissolved iron, and around 50% of this particulate iron was deemed to be potentially bioavailable, on the basis of experimental leaching. If our observations are scalable to the entire ice sheet, then the annual flux of dissolved and potentially bioavailable particulate iron to the North Atlantic Ocean would be approximately 0.3 Tg. This is comparable to dust-derived soluble iron inputs to the North Atlantic. We suggest that glacial runoff serves as a significant source of bioavailable iron to surrounding coastal oceans, which is likely to increase as melting of the Greenland ice sheet escalates under climate warming.
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Change history
29 April 2013
In the version of this Letter originally published, in the first sentence of the final paragraph, the 1992–2010 percentage increase in freshwater flux from the GrIS into the North Atlantic Ocean (as reported in ref. 25) was incorrectly stated to be 136%. The correct figure is 38%. This has been corrected in the PDF and HTML versions.
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Acknowledgements
This research was supported by: the WHOI Clark Arctic Research Initiative (E.B.K., S.B.D., M.A.C.), the National Science Foundation (M.A.C.), the WHOI Ocean and Climate Change Institute (M.P.B.), and an AGU Horton Hydrology Grant (M.P.B.). We are grateful to R. Allen for preliminary Fe analyses, to M. Gonneea and S. Birdwhistell for assistance with the ICP-MS analyses, to P. Lam, D. Ohnemus and B. Gready for helpful conversations, and to B. Gready, M. Evans and A. Criscitiello for their valuable assistance in the field.
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M.P.B., E.B.K., S.B.D. and M.A.C. designed the research. M.P.B., E.B.K., P.B.H. and M.A.C. collected the samples. M.P.B. and C.F.B. analysed the samples. M.P.B. and M.A.C. analysed the data. M.P.B., E.B.K., S.B.D. and M.A.C. wrote the paper.
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Bhatia, M., Kujawinski, E., Das, S. et al. Greenland meltwater as a significant and potentially bioavailable source of iron to the ocean. Nature Geosci 6, 274–278 (2013). https://doi.org/10.1038/ngeo1746
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DOI: https://doi.org/10.1038/ngeo1746
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