Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 4, issue 4
Biogeosciences, 4, 689–706, 2007
https://doi.org/10.5194/bg-4-689-2007
© Author(s) 2007. This work is licensed under
the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 License.
Biogeosciences, 4, 689–706, 2007
https://doi.org/10.5194/bg-4-689-2007
© Author(s) 2007. This work is licensed under
the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 License.

  23 Aug 2007

23 Aug 2007

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

L. Weber1, C. Völker2, A. Oschlies3, and H. Burchard4 L. Weber et al.
  • 1National Oceanography Centre, Southampton, UK
  • 2Alfred-Wegener-Institut für Polar- und Meeresforschung, Bremerhaven, Germany
  • 3Leibniz-Institut für Meereswissenschaften, Kiel, Germany
  • 4Institut für Ostseeforschung Warnemünde, Germany

Abstract. 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.

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