Surprisingly high dissolved iron (dFe) values have been found in the subsurface oxygen minimum waters of the tropical North Atlantic from the Cape Verde Islands west to 42°W, reaching concentrations of 1.0-1.5 nmol/kg. Fitzsimmons’ and co-authors results suggest that biological regeneration is a more consistent explanation for this enrichment than sedimentary diagenetic dFe mixed out from the African margin. The authors also mention the limits of artificial fertilizations, since their data demonstrates that high levels of surface Fe enrichment might be relatively ineffective as a means of removing carbon from the surface ocean.
Figure: This figure shows vertical dFe distribution in the upper 1000 m of the tropical North Atlantic Ocean. High dFe concentrations are in warm colours (red, orange,etc). Black dots represent sample locations. Please click here to see the figure larger.
Fitzsimmons, Jessica N., Ruifeng Zhang, Edward A. Boyle (2013) Dissolved iron in the tropical North Atlantic Ocean, Marine Chemistry, Volume: 154, 87-99, DOI:10.1016/j.marchem.2013.05.009