Comparative vertical distributions of iron in the Japan Sea, the Bering Sea, and the western North Pacific Ocean

Abstract

[1] The vertical distributions of dissolvable (unfiltered) Fe concentrations in semi-closed oceanic regions, such as the Japan Sea and the Bering Sea, are characterized by a gradual increase with depth in the intermediate and deep waters. However, there is a rapid decrease in the dissolvable Fe concentration over the narrow depth range between deep and bottom waters with constantly lower concentrations observed in the bottom waters of the Japan Sea (Japan Basin), probably from the injection of newly formed bottom water. In addition, the rapid increase in dissolvable Fe concentrations in bottom waters in the western North Pacific Ocean may be due to the resuspension of sediments from the seafloor or the slope. However, there are no differences of labile dissolved (

Controls on iron distributions in the deep water column of the North Pacific Ocean: Iron(III) hydroxide solubility and marine humic‐type dissolved organic matter

“…In the western North Pacific, the vertical Fe distributions and high [D‐Fe] and [P‐Fe] in intermediate and deep waters (Figures 4a–4c) were very similar to those at the same and nearby stations in previous studies [ Nakabayashi et al , 2001; Nishioka et al , 2003, 2007; Takata et al , 2005, 2006]. The high levels of [T‐Fe] and [P‐Fe] in intermediate and deep waters at the subtropical western North Pacific (station A‐3; Figure 4c) have also been observed at the nearby station in previous study [ Takata et al , 2005]. Moreover, much higher [D‐Fe] than [Fe(III)sol] in intermediate and deep waters have been usually observed in the western North Pacific in the present and previous studies [e.g., Nakabayashi et al , 2001; Takata et al , 2005].…”

“…Many studies of iron in the North Pacific Ocean have shown the detailed vertical distributions of the Fe concentration that have nutrient‐like profiles characterized by surface depletion due to biological uptake and middepth maxima due to remineralization of Fe‐rich biogenic matter [ Martin et al , 1989; Bruland et al , 1994; Nakabayashi et al , 2001; Nishioka et al , 2003; Takata et al , 2006]. In addition, many recent studies of the Fe(III) hydroxide solubility ([Fe(III)sol]) in seawater [ Kuma et al , 1996; Nakabayashi et al , 2001; Waite , 2001; Liu and Millero , 1999, 2002; Chen et al , 2004; Takata et al , 2005] suggest that [Fe(III)sol] is controlled by organic complexation, which plays an important role in regulating dissolved Fe concentrations ([D‐Fe]) in seawater [ van den Berg , 1995; Rue and Bruland , 1995, 1997; Johnson et al , 1997a, 1997b; Archer and Johnson , 2000; Kuma et al , 2003; Takata et al , 2005; Hiemstra and van Riemsdijk , 2006]. However, several recent studies of iron distributions revealed that [D‐Fe] (0.8–1.5 nM) in deep waters of the western North Pacific [ Nakabayashi et al , 2001; Takata et al , 2006; Nishioka et al , 2003, 2007] are approximately two times higher than those in the eastern and central North Pacific [ Martin et al , 1989; Bruland et al , 1994; Nishioka et al , 2003; Takata et al , 2006].…”

“…The most significant correlation was found between [Fe(III)sol] and H‐flu intensity in deep waters, suggesting that the distribution of humic‐type fluorescent dissolved organic matter (humic‐type FDOM) may control the distribution of [Fe(III)sol] in deep ocean waters. The [Fe(III)sol] profiles revealed that [D‐Fe] in deep waters may be controlled primarily by Fe(III) complexation with natural organic ligands, such as marine dissolved humic substances, released by the oxidative decomposition and transformation of biogenic organic matter in deep waters [ Takata et al , 2005]. In the deep water column of the western North Pacific Ocean, [D‐Fe] at each depth was usually to occur in excess of [Fe(III)sol].…”

Accumulation of humic-like fluorescent dissolved organic matter in the Japan Sea

“…Such high levels of DOC are possibly due to transport of semi-labile DOC from surface layers1 along with the JSPW formation. On the other hand, similar levels of FDOM H between the JSPW and the deep waters of the North Pacific were also reported34. DOM in the deep waters of the North Pacific can be characterized as lowest DOC concentration15 and highest levels of recalcitrant FDOM H 724 in the global deep ocean, indicative of the oldest DOM in the global ocean.…”

Temporal variability and bioavailability of iron and other nutrients during the spring phytoplankton bloom in the Oyashio region

“…(Obata et al, 1993) as reported in our previous studies (Takata et al, 2004(Takata et al, , 2005(Takata et al, , 2006(Takata et al, , 2008. Briefly, iron in a buffered sample solution was selectively collected on 8-hydroxyquinoline immobilized chelating resin and then eluted with dilute 0.3 N HCl.…”