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

L. Weber (1) , C. Völker (2) , A. Oschlies (3) , H. Burchard (4)

1 NOC - National Oceanography Centre [Southampton]
2 AWI - Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung = Alfred Wegener Institute for Polar and Marine Research = Institut Alfred-Wegener pour la recherche polaire et marine
3 IFM-GEOMAR - Leibniz-Institut für Meereswissenschaften
4 IOW - Leibniz-Institut für Ostseeforschung Warnemünde

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. Current estimates for these parameters 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. 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.

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]; Astrophysique [astro-ph]; Interfaces continentales, environnement; Océan, Atmosphère; Sciences de la Terre

L. Weber, C. Völker, A. Oschlies, H. Burchard. Iron profiles and speciation of the upper water column at the Bermuda Atlantic time-series Study site: a model based sensitivity study. Biogeosciences Discussions, 2007, 4 (2), pp.823-869. ⟨hal-00297878⟩