Solubility of iron in the Southern Ocean

• Published in: Limnology and Oceanography
• Main Authors: Schlosser, C., de La Rocha, Christina, Streu, P., Croot, Peter
• Other Authors: Leibniz-Institut für Meereswissenschaften (IFM-GEOMAR), National Oceanography Centre Southampton (NOC), University of Southampton, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Plymouth Marine Laboratory (PML)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2012
• Subjects: [SDE]Environmental Sciences; Antarctic; Prydz Bay; Southern Ocean; The Antarctic; Antarc*
• Online Access: https://hal.univ-brest.fr/hal-00710163; https://doi.org/10.4319/lo.2012.57.3.0684

International audience Iron solubility (cFe S) ranged from 0.4 to 1.5 nmol L -1, decreasing from south to north in three different Southern Ocean zones (the Coastal Zone, the Antarctic Zone, and the Polar Frontal Zone plus the Subantarctic Zone). This decrease was at times correlated with an increase in temperature. Organic Fe solubility (cFe S,org), which was obtained by subtracting from total measured Fe solubility the solubility of inorganic species of iron (Fe) at the measurement temperature (20°C), ranged from 0.3 to 1.3 nmol L -1, representing an average of 32 ± 14% of the concentration of ligands in the dissolved size fraction as determined via competitive ligand exchange- absorptive cathodic stripping voltammetry (barring a handful of extremely high values from a transect run to the east of Prydz Bay). Values of cFe S were mainly lower than the predicted value for inorganic Fe solubility at the in situ temperature. Total in situ Fe solubility (cFe S,adj) was therefore estimated by adjusting for inorganic Fe solubility at in situ temperatures (between -2°C and +18°C). Because in situ temperatures in the Antarctic Circumpolar Current were mostly lower than +3°C, such cFe S,adj values, ranging from 0.5 to 1.8 nmol L -1, were roughly twice as large as cFe S,org. The adjustment relies heavily on model calculations of inorganic Fe solubility but, if correct, indicates that the bulk of the solubility of Fe in the cold waters of the Southern Ocean is tied to the solubility of inorganic Fe rather than to Fe ligands in the soluble size fraction.