Water column iron dynamics in the North Pacific Ocean, bering sea and western arctic ocean

Abstract

Iron is an important biogeochemical trace element in the ocean. However, the stable oxidation state of iron in oxic seawater is Fe(III) with an extremely low solubility in seawater. Recent studies of the Fe(III) hydroxide solubility in seawater suggest that Fe(III) solubility is controlled by organic complexation, which plays an important role in regulating dissolved Fe concentrations in seawater. In this study, we attempted to confirm that the vertical distributions of dissolved Fe in deep water are controlled primarily by the Fe(III) solubility, which is regulated by Fe(III) complexation with natural organic ligands, comparing the characteristic vertical distributions of iron, nutrients, apparent oxygen utilization, and humictype fluorescence intensity in deep water of the North Pacific Ocean, Bering Sea and western Arctic Ocean. Dissolved Fe distributions in deep water column are mainly controlled by the production of dissolved Fe from particulate organic matter during carbon remineralization, the particle scavenging removal of dissolved Fe, and Fe(III) complexation with natural humic substances. Iron is generally supplied to surface water by upwelling, vertical water mixing, atmospheric and riverine inputs. In the western Arctic Ocean, the subsurface maxima of iron, nutrients, and humic substances were found in the halocline layer of slope and basin regions. The new finding results from the supply of chemical components from the continental-shelf sediments and lateral transport from the shelves to the Arctic basin. © 2013 The Japan Society for Analytical Chemistry.