High variability in dissolved iron concentrations in the vicinity of the Kerguelen Islands (Southern Ocean)

[摘要] Dissolved Fe (dFe) concentrations were measured in the upper 1300 m of thewater column in the vicinity of the Kerguelen Islands as part of the secondKErguelen Ocean Plateau compared Study (KEOPS2). Concentrations ranged from0.06 nmol L⁻¹ in offshore, Southern Ocean waters to 3.82 nmol L⁻¹within Hillsborough Bay, on the north-eastern coast of the Kerguelen Islands.Direct island runoff, glacial melting and resuspended sediments wereidentified as important inputs of dFe that could potentially fertilise thenorthern part of the plateau. A significant deep dFe enrichment was observedover the plateau with dFe concentrations increasing up to 1.30 nmol L⁻¹close to the seafloor, probably due to sediment resuspension and pore waterrelease. Biological uptake was shown to induce a significant decrease in dFeconcentrations between two visits (28 days apart) at a station above theplateau. Our work also considered other processes and sources, such aslateral advection of enriched seawater, remineralisation processes, and theinfluence of the polar front (PF) as a vector for Fe transport. Overall,heterogeneous sources of Fe over and off the Kerguelen Plateau, in additionto strong variability in Fe supply by vertical or horizontal transport, mayexplain the high variability in dFe concentrations observed during thisstudy.

[学科分类] 地球化学与岩石