Basin-scale transport of hydrothermal dissolved metals across the South Pacific Ocean

Journal name:
Nature
Volume:
523,
Pages:
200–203
Date published:
DOI:
doi:10.1038/nature14577
Received
Accepted
Published online

Hydrothermal venting along mid-ocean ridges exerts an important control on the chemical composition of sea water by serving as a major source or sink for a number of trace elements in the ocean1, 2, 3. Of these, iron has received considerable attention because of its role as an essential and often limiting nutrient for primary production in regions of the ocean that are of critical importance for the global carbon cycle4. It has been thought that most of the dissolved iron discharged by hydrothermal vents is lost from solution close to ridge-axis sources2, 5 and is thus of limited importance for ocean biogeochemistry6. This long-standing view is challenged by recent studies which suggest that stabilization of hydrothermal dissolved iron may facilitate its long-range oceanic transport7, 8, 9, 10. Such transport has been subsequently inferred from spatially limited oceanographic observations11, 12, 13. Here we report data from the US GEOTRACES Eastern Pacific Zonal Transect (EPZT) that demonstrate lateral transport of hydrothermal dissolved iron, manganese, and aluminium from the southern East Pacific Rise (SEPR) several thousand kilometres westward across the South Pacific Ocean. Dissolved iron exhibits nearly conservative (that is, no loss from solution during transport and mixing) behaviour in this hydrothermal plume, implying a greater longevity in the deep ocean than previously assumed6, 14. Based on our observations, we estimate a global hydrothermal dissolved iron input of three to four gigamoles per year to the ocean interior, which is more than fourfold higher than previous estimates7, 11, 14. Complementary simulations with a global-scale ocean biogeochemical model suggest that the observed transport of hydrothermal dissolved iron requires some means of physicochemical stabilization and indicate that hydrothermally derived iron sustains a large fraction of Southern Ocean export production.

At a glance

Figures

  1. Cruise track and station locations.
    Figure 1: Cruise track and station locations.

    The US GEOTRACES Eastern Pacific Zonal Transect (GEOTRACES cruise GP16) was undertaken on RV Thomas G. Thompson cruise 303 from 25 October to 20 December 2013. Station locations are shown as yellow circles with station numbers in white. Station 18 is located over the crest of the East Pacific Rise.

  2. Interpolated zonal concentration for GEOTRACES Eastern Pacific Zonal Transect.
    Figure 2: Interpolated zonal concentration for GEOTRACES Eastern Pacific Zonal Transect.

    a, Dissolved iron. b, Dissolved manganese. c, Dissolved aluminium. d, Excess helium-3 (3Hexs). Station numbers and distance west of East Pacific Rise are indicated on uppermost panel.

  3. Relationship between dissolved trace metals and 3He west of SEPR.
    Figure 3: Relationship between dissolved trace metals and 3He west of SEPR.

    a, Dissolved iron versus 3Hexs at 2,500 m depth (n = 11). b, Dissolved Fe versus 3Hexs, both integrated over a depth of 2,200–2,800 m except at station 18, where the maximum depth was 2,640 m (n = 9). c, Dissolved manganese versus 3Hexs at a depth of 2,500 m (n = 11). d, Dissolved manganese versus 3Hexs integrated as in b (n = 9). Error bars are twice the relative standard deviation of a given analysis, as reported in the Methods. Error bars are absent where the symbol size exceeds the error estimate. Lines represent the slope of a simple linear regression analysis of the data. Discrete and integrated 3Hexs concentrations are lower at station 18 relative to stations west of the ridge; this difference is reduced for integrations between 2,200 m and 2,640 m depth (Extended Data Fig. 1a). The relatively low 3Hexs concentrations at station 18 (˜15° S) suggest that the off-axis plume (stations 20–36) is primarily derived from vent fields located further south (˜17° S–18.5° S) on the SEPR5, 28 with hydrothermal and eruptive effluent being homogenized and transported north and west20 by along-axis and off-axis transport processes20, 30.

  4. Results of biogeochemical model simulations.
    Figure 4: Results of biogeochemical model simulations.

    Model simulation results centred at 2,530 m depth (average of two depth bins spanning 2,060–3,010 m; coloured lines) are shown in a and b. a, Dissolved Fe from model results compared to measured Fed concentrations (crosses) between 2,200 m and 2,800 m to the west of the ridge axis. b, Dissolved Fe versus 3Hexs from model simulations compared to measured values (diamonds) at 2,500 m depth. For a and b the individual model simulations were run for 75 years. Orange dashed line, model solution using base hydrothermal Fe flux (1 × Fe). Red dashed line, 10 × base hydrothermal Fe flux (10 × Fe). Cyan line, base hydrothermal Fe flux with equimolar flux of ligands (1 × Fe + 1 × ligands). Dark blue line, base hydrothermal Fe flux with 10 × greater ligand flux (1 × Fe + 10 × ligands). Green line, 10 × base Fe flux with equimolar flux of ligands (10 × Fe + 10 × ligands). c, Percentage of annual export production due to hydrothermal Fe based on a 500-year model simulation employing base hydrothermal Fe flux with equimolar ligand flux (1 × Fe + 1 × ligands) relative to a model solution with no hydrothermal Fe or ligand flux. Lower export production in the subtropical oceans is caused by decreased preformed macronutrients in the mode waters.

  5. Relationship between dissolved trace metals and 3HE.
    Extended Data Fig. 1: Relationship between dissolved trace metals and 3HE.

    Depth-integrated concentrations of dissolved Fe (a), and dissolved Mn (b), versus depth-integrated concentration of 3Hexs, over a depth range of 2,200–2,640 m. Sample station numbers are indicated for each data symbol.

  6. Comparison of modelled (rectangles) and measured (circular symbols) concentrations of 3Hexs, between EPZT cruise station 36 (far left) and station 17 (far right).
    Extended Data Fig. 2: Comparison of modelled (rectangles) and measured (circular symbols) concentrations of 3Hexs, between EPZT cruise station 36 (far left) and station 17 (far right).
  7. Sections of modelled Fed transport and decay using a dynamic ligand global-circulation model (see Methods).
    Extended Data Fig. 3: Sections of modelled Fed transport and decay using a dynamic ligand global-circulation model45 (see Methods).

    The model scenarios listed here are the same as those presented in Fig. 4. a, 1 × Fe; b, 10 × Fe; c, 1 × Fe + 1 × ligands; d, 1 × Fe + 10 × ligands; e, 10 × Fe + 10 × ligands.

  8. Impacts on carbon export from model simulations.
    Extended Data Fig. 4: Impacts on carbon export from model simulations.

    a, Percentage contribution to carbon export production due to the input of hydrothermal Fed, not considering the addition of hydrothermal ligands. b, Additional percentage contribution from the addition of hydrothermal ligands to the simulation shown in a. b represents the difference between the total impact from the addition of both hydrothermal Fed and ligands (see Fig. 4c) compared to the input hydrothermal Fed without the addition of the ligands shown in a.

  9. Ligand flux model experiments.
    Extended Data Fig. 5: Ligand flux model experiments.

    Two experiments were run to assess the impact of the flux of ligands associated with hydrothermal activity on the oceanic budget. a, Model simulation with no hydrothermal ligand flux. b, Model simulation with ligand flux equal to the flux of hydrothermal Fe.

Tables

  1. Model data comparison
    Extended Data Table 1: Model data comparison

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Author information

Affiliations

  1. Joint Institute for the Study of the Atmosphere and the Ocean, University of Washington and NOAA-PMEL, 7600 Sand Point Way NE, Seattle, Washington 98115, USA

    • Joseph A. Resing
  2. Department of Ocean, Earth and Atmospheric Sciences, Old Dominion University, Norfolk, Virginia 23529, USA

    • Peter N. Sedwick &
    • Bettina M. Sohst
  3. Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA

    • Christopher R. German &
    • William J. Jenkins
  4. Department of Biological Sciences, University of Southern California, 3616 Trousdale Parkway #AHF204, Los Angeles, California 90089, USA

    • James W. Moffett
  5. Department of Earth, Ocean and Ecological Sciences, School of Environmental Sciences, University of Liverpool, 4 Brownlow Street, Liverpool L69 3GP, UK

    • Alessandro Tagliabue

Contributions

J.A.R. participated on the EPZT and determined Ald and Mnd; P.N.S. interpreted the Fed data; C.R.G. co-designed the study and participated in the EPZT; W.J.J. collected 3Hexs data; J.W.M. co-designed the study, participated in the EPZT, and collected Fe(II) data; B.M.S. participated in the EPZT and determined Fed; A.T. conducted the modelling experiments and interpreted their results. All authors contributed to the writing of the manuscript.

Competing financial interests

The authors declare no competing financial interests.

Corresponding authors

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Author details

Extended data figures and tables

Extended Data Figures

  1. Extended Data Figure 1: Relationship between dissolved trace metals and 3HE. (159 KB)

    Depth-integrated concentrations of dissolved Fe (a), and dissolved Mn (b), versus depth-integrated concentration of 3Hexs, over a depth range of 2,200–2,640 m. Sample station numbers are indicated for each data symbol.

  2. Extended Data Figure 2: Comparison of modelled (rectangles) and measured (circular symbols) concentrations of 3Hexs, between EPZT cruise station 36 (far left) and station 17 (far right). (169 KB)
  3. Extended Data Figure 3: Sections of modelled Fed transport and decay using a dynamic ligand global-circulation model45 (see Methods). (631 KB)

    The model scenarios listed here are the same as those presented in Fig. 4. a, 1 × Fe; b, 10 × Fe; c, 1 × Fe + 1 × ligands; d, 1 × Fe + 10 × ligands; e, 10 × Fe + 10 × ligands.

  4. Extended Data Figure 4: Impacts on carbon export from model simulations. (467 KB)

    a, Percentage contribution to carbon export production due to the input of hydrothermal Fed, not considering the addition of hydrothermal ligands. b, Additional percentage contribution from the addition of hydrothermal ligands to the simulation shown in a. b represents the difference between the total impact from the addition of both hydrothermal Fed and ligands (see Fig. 4c) compared to the input hydrothermal Fed without the addition of the ligands shown in a.

  5. Extended Data Figure 5: Ligand flux model experiments. (206 KB)

    Two experiments were run to assess the impact of the flux of ligands associated with hydrothermal activity on the oceanic budget. a, Model simulation with no hydrothermal ligand flux. b, Model simulation with ligand flux equal to the flux of hydrothermal Fe.

Extended Data Tables

  1. Extended Data Table 1: Model data comparison (80 KB)

Comments

  1. Report this comment #66865

    Joseph Resing said:

    Please note that Reference 29 Farley et al., is incorrect. The global ^3^He efflux of 530 mol yr^-1^ comes from Bianchi et al 2010:
    Bianchi, D., J. L. Sarmiento, A. Gnanadesikan, R. M. Key, P. Schlosser, and R. Newton (2010), Low helium flux from the mantle inferred from simulations of oceanic helium isotope data, Earth and Planetary Science Letters, 297(3-4), 379-386. doi:10.1016/j.epsl.2010.06.03

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