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Enhanced Southern Ocean marine productivity due to fertilization by giant icebergs

Nature Geoscience volume 9, pages 219–221 (2016)Cite this article

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A Corrigendum to this article was published on 01 September 2016

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Abstract

Primary productivity is enhanced within a few kilometres of icebergs in the Weddell Sea1,2 owing to the input of terrigeneous nutrients and trace elements during iceberg melting. However, the influence of giant icebergs, over 18 km in length, on marine primary production in the Southern Ocean is less well studied1,3. Here we present an analysis of 175 satellite images of open ocean colour before and after the passage of 17 giant icebergs between 2003 and 2013. We detect substantially enhanced chlorophyll levels, typically over a radius of at least 4–10 times the iceberg’s length, that can persist for more than a month following passage of a giant iceberg. This area of influence is more than an order of magnitude larger than that found for sub-kilometre scale icebergs2 or in ship-based surveys of giant icebergs1. Assuming that carbon export increases by a factor of 5–10 over the area of influence, we estimate that up to a fifth of the Southern Ocean’s downward carbon flux originates with giant iceberg fertilization. We suggest that, if giant iceberg calving increases this century as expected4, this negative feedback on the carbon cycle may become more important.

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Figure 1: Chlorophyll-a concentration on 1 December 2013, from the MODIS Aqua satellite.
Figure 2: Mean chlorophyll level associated with the passage of a giant iceberg.
Figure 3: Chlorophyll concentration anomaly in the Pine Island Bay region of West Antarctica related to the passage of giant iceberg, B31.

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Change history

  • 16 August 2016

    In the version of this Letter originally published, it was incorrectly stated in Figure 1 that Chlorophyll-α concentrations were recorded on 12 January 2013, when the date should have been 1 December 2013. This has been corrected in the online versions of the paper.

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Acknowledgements

Much of this work followed from the MSc dissertation of L.P.A.M.D. We also acknowledge support for part of the work from the Natural Environment Research Council Urgency Grant NE/L010054/1, ‘Tracking and prediction of the giant Pine Island iceberg’, and SAR images from the German Aerospace Center Projects OCE2116 and 2184 and the European Space Agency project 16456. We wish to thank the Canadian Space Agency for providing the data from the latter ESA project. We also wish to thank E. Victor, who helped L.P.A.M.D. with some of the statistics, and J. Thompson, whose MSc research brought the comparisons shown in Fig. 3 to our attention.

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Authors and Affiliations

  1. Department of Geography, University of Sheffield, Sheffield S10 2TN, UK

    Luis P. A. M. Duprat, Grant R. Bigg & David J. Wilton

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  1. Luis P. A. M. Duprat
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Contributions

G.R.B. and L.P.A.M.D. conceived the project; L.P.A.M.D. carried out much of the analysis and assisted with writing; G.R.B. contributed to the analysis and was the principal writer of the final manuscript. D.J.W. carried out some of the tracking work shown in Fig. 3, and commented on the manuscript.

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Correspondence to Grant R. Bigg.

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The authors declare no competing financial interests.

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Duprat, L., Bigg, G. & Wilton, D. Enhanced Southern Ocean marine productivity due to fertilization by giant icebergs. Nature Geosci 9, 219–221 (2016). https://doi.org/10.1038/ngeo2633

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