References

Biogeosciences

1726-4189

Copernicus Publications

Göttingen, Germany

10.5194/bg-4-689-2007

Iron profiles and speciation of the upper water column at the Bermuda Atlantic Time-series Study site: a model based sensitivity study

Weber

¹ Völker

² Oschlies

³ Burchard

⁴

National Oceanography Centre, Southampton, UK

Alfred-Wegener-Institut für Polar- und Meeresforschung, Bremerhaven, Germany

Leibniz-Institut für Meereswissenschaften, Kiel, Germany

Institut für Ostseeforschung Warnemünde, Germany

23 08 2007

4 4 689 706

2007

This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 Generic License. To view a copy of this licence, visit https://creativecommons.org/licenses/by-nc-sa/2.5/

This article is available from https://bg.copernicus.org/articles/4/689/2007/bg-4-689-2007.html

The full text article is available as a PDF file from https://bg.copernicus.org/articles/4/689/2007/bg-4-689-2007.pdf

A one-dimensional model of the biogeochemistry and speciation of iron is coupled with the General Ocean Turbulence Model (GOTM) and a NPZD-type ecosystem model. The model is able to simulate the temporal patterns and vertical profiles of dissolved iron (dFe) in the upper ocean at the Bermuda Atlantic Time-series Study site reasonably well. Subsurface model profiles strongly depend on the parameter values chosen for the loss processes for iron, colloidal aggregation and scavenging onto particles. Estimates for these parameters based on observations in particle-rich waters result in depletion of dFe. A high stability constant of iron-binding organic ligands is required to reproduce the observed degree of organic complexation below the mixed layer. The scavenging residence time for iron in the model is shortest in spring and summer, because of the larger abundance of particles, and increases with depth towards values on the order of a hundred years. A solubility of atmospherically deposited iron higher than 2% lead to dFe concentrations incompatible with observations. Despite neglecting ultraviolet radiation, the model produces diurnal variations and mean vertical profiles of H2O2 and iron species that are in good agreement with observations.

References 1

Baker, A., Jickells, T., Witt, M., and Linge, K.: Trends in the solubility of iron, aluminium, manganese and phosphorus in aerosol collected over the Atlantic Ocean, Mar. Chem., 98, 43–58, 2006.

Barbeau, K. and Moffett, J.: Dissolution of iron oxides by phagotrophic protists: Using a novel method to quantify reaction rates, Environ. Sci. Technol., 32, 2969–2975, 1998.

Barbeau, K., Rue, E., Trick, C., Bruland, K., and Butler, A.: Photochemical reactivity of siderophores produced by marine heterotrophic bacteria and cyanobacteria based on characteristic Fe(III) binding groups, Limnol. Oceanogr., 48, 1069–1078, 2003.

Baskaran, M., Santschi, P., Benoit, G., and Honeyman, B.: Scavenging of thorium isotopes by colloids in seawater of the Gulf of Mexico, Geochimica et Cosmochimica Acta, 56, 3375–3388, 1992.

Bergquist, B. and Boyle, E.: Dissolved iron in the tropical and subtropical Atlantic Ocean, Global Biogeochem. Cy., 20, GB1015, https://doi.org/10.1029/2005GB002 505, 2006.

Brock, T. D.: Calculating solar radiation for ecological studies, Ecol. Model., 14, 1–19, 1981.

Bruggeman, J., Burchard, H., Kooi, B., and Sommeijer, B.: A second-order, unconditionally stable, mass-conserving integration scheme for biochemical systems, Appl. Numer. Math., 57, 36–58, 2006.

Burchard, H., Deleersnijder, E., and Meister, A.: Application of Modified Patankar schemes to stiff biogeochemical models for the water column, Ocean Dynam., 55, 326–337, 2005.

Burchard, H., Bolding, K., Kuehn, W., Meister, A., Neumann, T., and Umlauf, L.: Description of a flexible and extendable physical-biogeochemical model system for the water column, J. Mar. Syst., 61, 180–211, 2006.

Carlson, C., Ducklow, H. W., and Michaels, A. F.: Annual flux of dissolved organic-carbon from the euphotic zone in the northwestern Sargasso Sea, Nature, 371, 405–408, 1994.

Cheng, Y., Canuto, V M., and Howard, A M.: An improved model for the turbulent PBL, J. Atmos. Sci., 59, 1550–1565, 2002.

Cullen, J., Berquist, B., and Moffett, J.: Thermodynamic characterization of partitioning of iron between soluble and colloidal species in the Atlantic Ocean, Mar. Chem., 98, 295–303, 2006.

Doney, S., Najjar, R., and Stewart, S.: Photochemistry, mixing and diurnal cycles in the upper ocean, J. Mar. Res., 53, 341–369, 1995.

Droop, M R.: 25 years of algal growth kinetics: a personal view, Botanica Marina, 26, 99–112, 1983.

Duce, R. and Tindale, N.: Atmospheric transport of iron and its deposition in the ocean, Limnol. Oceanogr., 36, 1715–1726, 1991.

Dutkiewicz, S., Follows, M J., and Parekh, P.: Interactions of the iron and phosphorus cycles: A three-dimensional model study, Global Biogeochem. Cy., 19, 1–22, 2005.

Emmenegger, L., Schönberger, R., Sigg, L., and Sulzberger, B.: Light-induced redox cycling of iron in circumneutral lakes, Limnol. Oceanogr., 46, 49–61, 2001.

Fung, I., Meyn, S., Tegen, I., Doney, S., John, J., and Bishop, J.: Iron supply and demand in the upper ocean, Global Biogeochem. Cy., 14, 281–301, 2000.

Gledhill, M. and van den Berg, C.: Determination of complexation of iron(III) with natural organic complexing ligands in seawater using cathodic stripping voltammetry, Mar. Chem., 47, 41–54, 1994.

Jerlov, N.: Optical oceanography, Elsevier, 1968.

Jickells, T. and Spokes, L.: Atmospheric iron inputs to the oceans, in: The Biogeochemistry of Iron in Seawater, edited by: Turner, D. and Hunter, K., SCOR/IUPAC Series, J. Wiley, 85–121, 2001.

Johnson, K., Coale, K., Elrod, V., and Tindale, N.: Iron photochemistry in seawater from the equatorial Pacific, Mar. Chem., 46, 319–334, 1994.

Johnson, K., Gordon, R., and Coale, K.: What controls dissolved iron concentrations in the world ocean?, Mar. Chem., 57, 137–161, 1997.

King, D., Aldrich, R., and Charniecki, S.: Photochemical redox cycling of iron in NaCl solutions, Mar. Chem., 44, 105–120, 1993.

Kuma, K., Nakabayashi, S., Suzuki, Y., Kudo, I., and Matsunaga, K.: Photo-reduction of Fe(III) by dissolved organic substances and existence of Fe(II) in seawater during spring blooms, Mar. Chem., 37, 15–27, 1992.

Mahowald, N., Luo, C., Del~Corral, J., and Zender, C.: Interannual variability in atmospheric mineral aerosols from a 22-year model simulation and observational data, J. Geophys. Res., 108(D12), 4352, https://doi.org/10.1029/2002JD002821, 2003.

McClain, C. and Firestone, J.: An investigation of Ekman upwelling in the North Atlantic, J. Geophys. Res., 98, 12 327–12 339, 1993.

Moffet, J.: Transformations among different forms of iron in the ocean, in: The Biogeochemistry of Iron in Seawater, edited by: Turner, D. and Hunter, K., SCOR/IUPAC Series, J. Wiley, 1–7, 2001.

Moran, S B. and Buesseler, K O.: Short residence time of colloids in the upper ocean off Bermuda, Nature, 359, 221–223, 1992.

Musgrave, D., Chow, J., and Jenkins, W.: Application of a model of upper-ocean physics for studying seasonal cycles of oxygen, J. Geophys. Res., 93, 15 679–15 700, 1988.

Nishioka, J., Takeda, S., de~Baar, H J., Croot, P L., Boye, M., Laan, P., and Timmermans, K R.: Changes in the concentration of iron in different size fractions during an iron enrichment experiment in the open Southern Ocean, Mar. Chem., 95, 51–63, 2005.

Obernosterer, I., Ruardij, P., and Herndl, G.: Spatial and diurnal dynamics of dissolved organic matter (DOM) fluorescence and H2O2 and the photochemical demand of surface water DOM across the subtropical Atlantic Ocean, Limnol. Oceanogr., 46, 632–643, 2001.

Ono, S., amd R.G Najjar, A E., and Bates, N.: Shallow remineralization in the Sargasso Sea estimated from seasonal variations in oxygen, dissolved inorganic carbon and nitrate, Deep-Sea Res. II, 48, 1567–1582, 2001.

Oschlies, A. and Schartau, M.: Basin-scale performance of a locally optimized marine ecosystem model, J. Mar. Res., 63, 335–358, 2005.

Parekh, P., Follows, M., and Boyle, E.: Modelling the global ocean iron cycle, Global Biogeochem. Cy., 18, GB1002, \doi1029/2003GB002061, 2004.

Paulson, C A. and Simpson, J J.: Irradiance measurements in the upper ocean, J. Phys. Oceanogr., 7, 952–956, 1977.

Rijkenberg, M., Fischer, A., Kroon, J., Gerringa, L., Timmermans, K., Wolterbeek, H., and de~Baar, H.: The influence of UV irradiation on the photoreduction of iron in the Southern Ocean, Mar. Chem., 93, 119–129, 2005.

Rijkenberg, M. J A., Gerringa, L. J A., Neale, P J., Timmermans, K R., Buma, A. G J., and Baar, H. J. W d.: UVA variability overrules UVB ozone depletion effects on the photoreduction of iron in the Southern Ocean, Geophys. Res. Lett., 31, 1–5, 2004.

Rose, A. and Waite, T.: Predicting iron speciation in coastal waters from the kinetics of sunlight-mediated iron redox cycling, Aquat. Sci., 65, 375–383, 2003.

Rue, E. and Bruland, K.: Complexation of iron(III) by natural organic ligands in the Central North Pacific as determined by a new competitive ligand equilibration / adsorptive cathodic stripping voltammetric method, Mar. Chem., 50, 117–138, 1995.

Schartau, M. and Oschlies, A.: Simultaneous data-based optimization of a 1D-ecosystem model at three locations in the North Atlantic: Part I – Method and parameter estimates, J. Mar. Res., 61, 765–793, 2003.

Sedwick, P., Church, T., Bowie, A., Marsay, C., Ussher, S., Achilles, K., Lethaby, P., Johnson, R., Sarin, M., and McGillicuddy, D.: Iron in the Sargasso Sea (BATS region) during summer: Eolian imprint, spatiotemporal variability, and ecological implications, Global Biogeochem. Cy., 19, GB4006, https://doi.org/10.1029/2004GB002445, 2005.

Smith, R. and Baker, K.: Penetration of UV-B and biologically effective dose-rates in natural waters, Photochem. Photobiol., 29, 311–323, 1979.

Spokes, L. and Jickells, T.: Factors controlling the solubility of aerosol trace metals in the atmosphere and on mixing into seawater, Aquat. Geochem., 1, 355–374, 1996.

Steinberg, D., Carlson, C., Bates, N., Johnson, R. J., and Michaels, A. A. K.: Overview of the US JGOFS Bermuda Atlantic Time-series Study (BATS): A decade-scale look at ocean biology and biogeochemistry, Deep-Sea Res. II, 48, 1405–1447, 2001.

Sunda, W. and Huntsman, S.: Iron uptake and growth limitation in oceanic and coastal phytoplankton, Mar. Chem., 50, 189–206, 1995.

Umlauf, L. and Burchard, H.: Second-order turbulence models for geophysical boundary layers. A review of recent work, Cont. Shelf Res., 25, 795–827, 2005.

Uppala, S., Kallberg, P., Simmons, A., Andrae, U., da~Costa~Bechtold, V., Fiorino, M., Gibson, J., Haseler, J., Hernandez, A., Kelly, G., Li, X., Onogi, K., Saarinen, S., Sokka, N., Allan, R., Andersson, E., Arpe, K., Balmaseda, M., Beljaars, A., van~de Berg, L., Bidlot, J., Bormann, N., Caires, S., Chevallier, F., Dethof, A., Dragosavac, M., Fisher, M., Fuentes, M., Hagemann, S., Holm, E., Hoskins, B., Isaksen, L., Janssen, P., Jenne, R., McNally, A., Mahfouf, J.-F., Morcrette, J.-J., Rayner, N., Saunders, R., Simon, P., Sterl, A., Trenberth, K., Untch, A., Vasiljevic, D., Viterbo, P., and Woollen, J.: The ERA-40 re-analysis, Q. J. Roy. Meteor. Soc., 131, 2961–3012, 2005.

Van~den Berg, C.: Evidence for organic complexation of iron in seawater, Mar. Chem., 50, 139–157, 1995.

Voelker, B. and Sedlak, D.: Iron reduction by photoproduced superoxide in seawater, Mar. Chem., 50, 93–102, 1995.

Waite, T. and Morel, F.: Photoreductive dissolution of colloidal iron oxides in natural waters, Environ. Sci. Technol., 18, 860–868, 1984.

Watson, A.: Iron limitation in the ocean, in: The Biogeochemistry of Iron in Seawater, edited by: Turner, D. and Hunter, K., SCOR/IUPAC Series, J. Wiley, Chichester, 9–39, 2001.

Weber, L., Völker, C., Schartau, M., and Wolf-Gladrow, D.: Modeling the speciation and biogeochemistry of iron an the Bermuda Atlantic Timeseries Study site, Global Biogeochem. Cy., 19, GB1019, https://doi.org/10.1029/2004GB002340, 2005.

Wells, M.: Marine Colloids and Trace Metals, in: Marine Dissolved Organic Matter, edited by: Hansell, D. A. and Carlson, C. A., Academic Press, Elsevier, 367–404, 2002.

Wells, M. and Mayer, L.: The photoconversion of colloidal iron oxyhydroxides in seawater, Deep-Sea-Res., 38, 1379–1395, 1991.

Wen, L.-S., Santschi, P., and Tang, D.: Interactions between radioactively labeled colloids and natural particles: Evidence for colloidal pumping, Geochimica et Cosmochimica Acta, 61, 2867–2878, 1997.

Witter, A. and Luther III, G.: Variation in Fe-organic complexation with depth in the northwestern Atlantic Ocean as determined using a kinetic approach, Mar. Chem., 62, 241–258, 1998.

Witter, A., Hutchins, D., Butler, A., and Luther III, G.: Determination of conditional stability constants and kinetic constants for strong model Fe-binding ligands in seawater, Mar. Chem., 69, 1–17, 2000.

Wu, J. and Boyle, E.: Determination of iron in seawater by high-resolution isotope dilution inductively coupled plasma mass spectrometry after Mg(OH)2 coprecipitation, Analytica Chimica Acta, 367, 183–191, 1998.

Wu, J. and Boyle, E.: Iron in the Sargasso Sea: Implications for the processes controlling dissolved Fe distribution in the ocean, Global Biogeochem. Cy., 16, 1086, \doi10.1029/2001GB001453, 2002.

Wu, J. and Luther III, G.: Size-fractionated iron concentrations in the water column of the western North Atlantic Ocean, Limnol. Oceanogr., 39, 1119–1129, 1994.

Wu, J. and Luther III, G.: Complexation of Fe(III) by natural organic ligands in the Northwest Atlantic Ocean by a competitive ligand equilibration method and a kinetic approach, Mar. Chem., 50, 159–177, 1995.

Wu, J., Boyle, E., Sunda, W., and Wen, L.-S.: Soluble and colloidal iron in the oligotrophic North Atlantic and North Pacific, Science, 293, 847–849, 2001.

Zhuang, G., Duce, R., and Kester, D.: The dissolution of atmospheric iron in the surface seawater of the open ocean, J. Geophys. Res., 95, 16 207–16 216, 1990.