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Gulf Stream rings as a source of iron to the North Atlantic subtropical gyre

Nature Geosciencevolume 11pages594598 (2018) | Download Citation


Substantial amounts of nitrogen fixation occur in the North Atlantic subtropical gyre, due to the activity of cyanobacteria with high iron requirements. Iron is delivered to this region by dust from the Sahara Desert. However, this dust deposition is typically localized and episodic. Therefore, other sources of iron may also be important. Here, we report observations of dissolved iron concentrations in a Gulf Stream cold-core ring, which transported iron-rich water from near the continental slope into the subtropical gyre. We find that iron concentrations were elevated in the ring compared with subtropical waters, reflecting its source waters. Using iron data from these source waters and the identification of ring activity in satellite data, we estimate that cold-core rings provide a net flux of 0.3 ± 0.17 × 108 mol Fe yr−1 across the northwestern gyre edge, on the order of 15% of our median estimates of gyre-wide supply of iron by dust deposition. We suggest that iron supply from cold-core rings is an important source of iron to the northwestern gyre edge. We conclude that mesoscale ocean circulation features may play an important role in subtropical nutrient and carbon cycling.

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  1. 1.

    Boyd, P. W. et al. Mesoscale iron enrichment experiments 1993-2005: synthesis and future directions. Science 315, 612–617 (2007).

  2. 2.

    Moore, C. M. et al. Processes and patterns of oceanic nutrient limitation. Nat. Geosci. 6, 701–710 (2013).

  3. 3.

    Tagliabue, A. et al. The integral role of iron in ocean biogeochemistry. Nature 543, 51–59 (2017).

  4. 4.

    Mahowald, N. M. et al. Atmospheric global dust cycle and iron inputs to the ocean. Glob. Biogeochem. Cycles 19, GB4024 (2005).

  5. 5.

    Sedwick, P. N. et al. Iron in the Sargasso Sea (Bermuda Atlantic Time-Series Study region) during summer: eolian imprint, spatiotemporal variability, and ecological implications. Global Biogeochem. Cycles 19, GB4006 (2005).

  6. 6.

    Gruber, N. & Sarmiento, J. L. Global patterns of marine nitrogen fixation and denitrification. Global Biogeochem. Cycles 11, 235–266 (1997).

  7. 7.

    Geider, R. J. & La Roche, J. The role of iron in phytoplankton photosynthesis, and the potential for iron-limitation of primary productivity in the sea. Photosynth. Res. 39, 275–301 (1994).

  8. 8.

    Jickells, T. D., Baker, A. R. & Chance, R. Atmospheric transport of trace elements and nutrients to the oceans. Phil. Trans. R. Soc. Lond. A 374, 20150286 (2016).

  9. 9.

    Moxim, W. J., Fan, S.-M. & Levy, H. The meteorological nature of variable soluble iron transport and deposition within the North Atlantic Ocean basin. J. Geophys. Res. 116, D03203 (2011).

  10. 10.

    Conway, T. M. & John, S. G. Quantification of dissolved iron sources to the North Atlantic Ocean. Nature 511, 212–215 (2014).

  11. 11.

    Moore, C. M. et al. Iron limits primary productivity during spring bloom development in the central North Atlantic. Global Change Biol. 12, 626–634 (2006).

  12. 12.

    Browning, T. J. et al. Iron limitation of microbial phosphorus acquisition in the tropical North Atlantic. Nat. Commun. 8, 15465 (2017).

  13. 13.

    Olson, D. B. Rings in the ocean. Ann. Rev. Earth. Planet. Sci. 19, 283–311 (1991).

  14. 14.

    Palter, J. B., Lozier, M. S., Sarmiento, J. L. & Williams, R. G. The supply of excess phosphate across the Gulf Stream and the maintenance of subtropical nitrogen fixation. Global Biogeochem. Cycles 25, GB4007 (2011).

  15. 15.

    Williams, R. G. & Follows, M. J. The Ekman transfer of nutrients and maintenance of new production over the North Atlantic. Deep-Sea Res. Part I 45, 461–489 (1998).

  16. 16.

    Williams, R. G. et al. Nutrient streams in the North Atlantic: advective pathways of inorganic and dissolved organic nutrients. Global Biogeochem. Cycles 25, GB4008 (2011).

  17. 17.

    Williams, R. G., Roussenov, V. & Follows, M. J. Nutrient streams and their induction into the mixed layer. Global Biogeochem. Cycles 20, GB1016 (2006).

  18. 18.

    Letscher, R. T., Primeau, F. F. & Moore, J. K. Nutrient budgets in the subtropical ocean gyres dominated by lateral transport. Nat. Geosci. 9, 815–819 (2016).

  19. 19.

    Faghmous, J. H. et al. A daily global mesoscale ocean eddy dataset from satellite altimetry. Sci. Data 2, 150028 (2015).

  20. 20.

    Mawji, E. et al. The GEOTRACES Intermediate Data Product 2014. Mar. Chem. 177, 1–8 (2015).

  21. 21.

    Jenkins, W. J., Smethie, W. M., Boyle, E. A. & Cutter, G. A. Water mass analysis for the US GEOTRACES (GA03) North Atlantic sections. Deep-Sea Res. Part II 116, 6–20 (2015).

  22. 22.

    Townsend, D. W. & Ellis, W. G. in Carbon and Nutrient Fluxes in Continental Margins: A Global Synthesis (eds Liu, K.-K. et al.) 7234–7248 (Springer, Berlin, Heidelberg 2010).

  23. 23.

    Palter, J. B., Lozier, M. S. & Barber, R. T. The effect of advection on the nutrient reservoir in the North Atlantic subtropical gyre. Nature 437, 687–692 (2005).

  24. 24.

    Rijkenberg, M. J. A. et al. The distribution of dissolved iron in the West Atlantic Ocean. PLoS ONE 9, e101323 (2014).

  25. 25.

    Middag, R. et al. Intercomparison of dissolved trace elements at the Bermuda Atlantic Time Series station. Mar. Chem. 177, 476–489 (2015).

  26. 26.

    Conway, T. M., John, S. G. & Lacan, F. Intercomparison of dissolved iron isotope profiles from reoccupation of three GEOTRACES stations in the Atlantic Ocean. Mar. Chem. 183, 50–61 (2016).

  27. 27.

    Wu, J. & Luther, G. W. Spatial and temporal distribution of iron in the surface water of the northwestern Atlantic Ocean. Geochim. Cosmochim. Acta 60, 2729–2741 (1996).

  28. 28.

    Conway, T. M. & John, S. G. The cycling of iron, zinc and cadmium in the North East Pacific Ocean—insights from stable isotopes. Geochim. Cosmochim. Acta 164, 262–283 (2015).

  29. 29.

    Bower, A. S., Rossby, H. T. & Lillibridge, J. L. The Gulf Stream: barrier or blender? J. Phys. Ocean. 15, 24–32 (1985).

  30. 30.

    Qiu, B., Chen, S. & Hacker, P. Effect of mesoscale eddies on subtropical mode water variability from the Kuroshio Extension System Study (KESS). J. Phys. Oceanogr. 37, 982–1000 (2007).

  31. 31.

    Lai, D. Y., Richardson, P. L., Lai, D. Y. & Richardson, P. L. Distribution and movement of Gulf Stream rings. J. Phys. Oceanogr. 7, 670–683 (1977).

  32. 32.

    Buck, K., Sohst, B. M. & Sedwick, P. N. The organic complexation of dissolved iron along the US GEOTRACES (GA03) North Atlantic Section. Deep-Sea Res. Part II 116, 152–165 (2015).

  33. 33.

    Fishwick, M. P. et al. The impact of changing surface ocean conditions on the dissolution of aerosol iron. Global Biogeochem. Cycles 28, 1235–1250 (2014).

  34. 34.

    Moreno, A. R. & Martiny, A. C. Ecological stoichiometry of ocean plankton. Ann. Rev. Mar. Sci. 10, 43–69 (2018).

  35. 35.

    Deutsch, C., Sarmiento, J. L., Sigman, D. M., Gruber, N. & Dunne, J. P. Spatial coupling of nitrogen inputs and losses in the ocean. Nature 445, 163–167 (2007).

  36. 36.

    Ward, B. A., Dutkiewicz, S., Moore, C. M. & Follows, M. J. Iron, phosphorus, and nitrogen supply ratios define the biogeography of nitrogen fixation. Limnol. Oceanogr. 58, 2059–2075 (2013).

  37. 37.

    Tilman, D. Resource competition between plankton algae: an experimental and theoretical approach. Ecology 58, 338–348 (1977).

  38. 38.

    Twining, B. S. & Baines, S. B. The trace metal composition of marine phytoplankton. Ann. Rev. Mar. Sci. 5, 191–215 (2013).

  39. 39.

    Conway, T. M. & John, S. G. The biogeochemical cycling of zinc and zinc isotopes in the North Atlantic Ocean. Global Biogeochem. Cycles 28, 1111–1128 (2014).

  40. 40.

    Shaked, Y., Xu, Y., Leblanc, K. & Morel, F. M. M. Zinc availability and alkaline phosphatase activity in Emiliania huxleyi: implications for Zn–P co-limitation in the ocean. Limnol. Oceanogr. 51, 299–309 (2006).

  41. 41.

    Mahaffey, C., Reynolds, S., Davis, C. E. & Lohan, M. C. Alkaline phosphatase activity in the subtropical ocean: insights from nutrient, dust and trace metal addition experiments. Front. Mar. Sci. 1, 73 (2014).

  42. 42.

    Orcutt, K., Gundersen, K. & Ammerman, J. Intense ectoenzyme activities associated with Trichodesmium colonies in the Sargasso Sea. Mar. Ecol. Prog. Ser. 478, 101–113 (2013).

  43. 43.

    Sohm, J. A., Mahaffey, C. & Capone, D. G. Assessment of relative phosphorus limitation of Trichodesmium spp. in the North Pacific, North Atlantic, and the north coast of Australia. Limnol. Oceanogr. 53, 2495–2502 (2008).

  44. 44.

    Xiu, P., Palacz, A. P., Chai, F., Roy, E. G. & Wells, M. L. Iron flux induced by Haida eddies in the Gulf of Alaska. Geophys. Res. Lett. 38, L13607 (2011).

  45. 45.

    Richardson, P. L., Cheney, R. E. & Worthington, L. V. A census of Gulf Stream rings, spring 1975. J. Geophys. Res. 83, 6136–6144 (1978).

  46. 46.

    de Boyer Montégut, C., Madec, G., Fischer, A. S., Lazar, A. & Iudicone, D. Mixed layer depth over the global ocean: an examination of profile data and a profile-based climatology. J. Geophys. Res. 109, C12003 (2004).

  47. 47.

    LaCasce, J. H. Statistics from Lagrangian observations. Prog. Oceanogr. 77, 1–29 (2008).

  48. 48.

    The Climode Group. The Climode field campaign: observing the cycle of convection and restratification over the Gulf Stream. Bull. Am. Meteorol. Soc. 90, 1337–1350 (2009).

  49. 49.

    Trapp, J. M., Millero, F. J. & Prospero, J. M. Trends in the solubility of iron in dust-dominated aerosols in the equatorial Atlantic trade winds: importance of iron speciation and sources. Geochem. Geophys. Geosyst. 11, Q03014 (2010).

  50. 50.

    Shelley, R. U., Morton, P. & Landing, W. M. Elemental ratios and enrichment factors in aerosols from the US-GEOTRACES North Atlantic transects. Deep-Sea Res. Part II 116, 262–272 (2015).

  51. 51.

    Patey, M. D., Achterberg, E. P., Rijkenberg, M. J. & Pearce, R. Aerosol time-series measurements over the tropical Northeast Atlantic Ocean: dust sources, elemental composition and mineralogy. Mar. Chem. 174, 103–119 (2015).

  52. 52.

    Taylor, S. R. & McLennan, S. M. The Continental Crust: Its Composition and Evolution (Blackwell Scientific Publishing, Oxford, 1985).

  53. 53.

    Anderson, R. F. et al. How well can we quantify dust deposition to the ocean? Phil. Trans. R. Soc. Lond. A 374, 20150285 (2016).

  54. 54.

    Measures, C. I., Hatta, M., Fitzsimmons, J. N. & Morton, P. Dissolved Al in the zonal N Atlantic section of the US GEOTRACES 2010/2011 cruises and the importance of hydrothermal inputs. Deep-Sea Res. Part II 116, 176–186 (2015).

  55. 55.

    Baker, A. R., Adams, C., Bell, T. G., Jickells, T. D. & Ganzeveld, L. Estimation of atmospheric nutrient inputs to the Atlantic Ocean from 50°N to 50°S based on large-scale field sampling: iron and other dust-associated elements. Global Biogeochem. Cycles 27, 755–767 (2013).

  56. 56.

    Powell, C. F. et al. Estimation of the atmospheric flux of nutrients and trace metals to the eastern tropical North Atlantic Ocean. J. Atmos. Sci. 72, 4029–4045 (2015).

  57. 57.

    Sholkovitz, E. R., Sedwick, P. N., Church, T. M., Baker, A. R. & Powell, C. F. Fractional solubility of aerosol iron: synthesis of a global-scale data set. Geochim. Cosmochim. Acta 89, 173–189 (2012).

  58. 58.

    Luo, C. et al. Combustion iron distribution and deposition. Global Biogeochem. Cycles 22, GB1012 (2008).

  59. 59.

    Albani, S. et al. Paleodust variability since the Last Glacial Maximum and implications for iron inputs to the ocean. Geophys. Res. Lett. 43, 3944–3954 (2016).

  60. 60.

    Albani, S. et al. Improved dust representation in the Community Atmosphere Model. J. Adv. Model. Earth Syst. 6, 541–570 (2014).

  61. 61.

    Zhang, Y. et al. Modeling the global emission, transport and deposition of trace elements associated with mineral dust. Biogeosci. Discuss. 11, 17491–17541 (2015).

  62. 62.

    Wang, R. et al. Sources, transport and deposition of iron in the global atmosphere. Atmos. Chem. Phys. 15, 6247–6270 (2015).

  63. 63.

    Ito, A. & Shi, Z. Delivery of anthropogenic bioavailable iron from mineral dust and combustion aerosols to the ocean. Atmos. Chem. Phys. 16, 85–99 (2016).

  64. 64.

    Conway, T. M., Wolff, E. W., Röthlisberger, R., Mulvaney, R. & Elderfield, H. E. Constraints on soluble aerosol iron flux to the Southern Ocean at the Last Glacial Maximum. Nat. Commun. 6, 7850 (2015).

  65. 65.

    Longo, A. F. et al. Influence of atmospheric processes on the solubility and composition of iron in Saharan dust. Environ. Sci. Technol. 50, 6912–6920 (2016).

  66. 66.

    Schlitzer, R. et al. The GEOTRACES Intermediate Data Product 2017. Chem. Geol. (2018).

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We thank all those who contributed to the US GEOTRACES GA03 cruises; scientists from the US GEOTRACES Program and the Ocean Data Facility who measured the trace metals, nutrients and physical parameters for the USGT11 cruise used in this study; N. Mahowald, S. Albani, A. Ito and R. Wang for making model output available; and P. Sedwick, W. Landing, N. Mahowald, C. Measures and D. Vance for useful discussions. T.M.C. acknowledges support from the University of South Florida; J.B.P. acknowledges support from the University of Rhode Island; G.F.d.S. is supported by the European Union’s Horizon 2020 research and innovation programme under Marie Skłodowska-Curie grant agreement #708407.

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Author notes

  1. These authors contributed equally: Tim M. Conway, Jaime B. Palter, Gregory F. de Souza.


  1. College of Marine Science and School of Geosciences, University of South Florida, St Petersburg, FL, USA

    • Tim M. Conway
  2. Institute of Geochemistry and Petrology, ETH Zürich, Department of Earth Sciences, Zürich, Switzerland

    • Tim M. Conway
    •  & Gregory F. de Souza
  3. School of Oceanography, University of Rhode Island, Narragansett, RI, USA

    • Jaime B. Palter


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All authors contributed equally to this work. T.M.C. and G.F.d.S. conceived the idea, J.B.P. carried out the ring-driven Fe transport calculations and G.F.d.S. carried out the atmospheric deposition calculations.

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The authors declare no competing interests.

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Correspondence to Tim M. Conway.

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