Organic Fe speciation in the Eurasian Basins of the Arctic Ocean and its relation to terrestrial DOM

Abstract

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Dissolved Fe in the Deep and Upper Arctic Ocean With a Focus on Fe Limitation in the Nansen Basin

“…(0.5-4.42 nM, Stations 81-101; Figures 4B,C, 6A). Silicate and phosphate were also high in the TPD whereas nitrate was only slightly elevated compared to the same depths outside the TPD (Slagter et al, 2017). Station 117 at the rim of the TPD had lower DFe concentrations of 0.51-1.81 nM, whereas at Station 134 outside the TPD, DFe was even lower with 0.32-0.62 nM at depths <100 m (Figures 4B,C, 6A).…”

“…All measurements were calibrated with standards diluted in low nutrient seawater, which was also used as wash-water between the samples. A lab reference cocktail (Slagter et al, 2017). Stations numbers are given in three transects, 1-3, the arrows give the direction in which transects are presented in Figures 2, 5-9.…”

“…The hydrography of the Transects I and II is described by Slagter et al (2017) using definitions by Rudels (2010Rudels ( , 2012 and is repeated here briefly (Figures 2A,B). The Polar Surface Water (PSW) influenced by sea ice melt and river water is characterized by potential temperatures <0 • C and salinities <34.5.…”

“…In the Amundsen and Makarov Basins, DFe in the upper 100 m was high within the boundaries of the TPD, defined after Slagter et al (2017) as in-situ CDOM fluorescence ≥ 0.5 a.u. (0.5-4.42 nM, Stations 81-101; Figures 4B,C, 6A).…”

“…River discharge in the shelf-surrounded Arctic Ocean is a source of nutrients. These nutrients, including dissolved Fe (DFe) complexed by humic organic ligands (Laglera and van den Berg, 2009;Slagter et al, 2017), are transported in the upper 50 m through the Arctic Ocean by the transpolar drift (TPD) from the Eurasian rivers over the central Arctic to Fram Strait (Gordienko and Laktionov, 1969;Gregor et al, 1998). The TPD track varies annually depending on the Arctic Oscillation index (Macdonald et al, 2005).…”