5:15 PM - 6:45 PM
[ACG42-P10] A comparison of iron and manganese distributions in the East Siberian Arctic Seas
Iron (Fe) and manganese (Mn) are redox-sensitive metals and share common sources in the Arctic surface waters. The East Siberian Arctic Seas (ESAS) receives large amounts of freshwater from Arctic rivers (e.g., Lena River), as well as meltwater from sea ice. In addition, the wide East Siberian shelf provides significant margin fluxes of sediments in the ESAS. Because the ESAS remains one of the less studied areas of the Arctic Ocean, metal inputs from these sources into the surface ESAS remain unknown. In this study, we present data on Fe and Mn in the surface waters of the ESAS and discuss their potential sources.
Observation in the ESAS was carried out in cooperation with the Nansen and Amundsen Basins Observational System (NABOS) expedition in September−October 2021. Surface water samples were collected at a depth of approximately 10 m using a peristaltic pump. Dissolved Fe (dFe) and Mn (dMn) in the samples were pre-concentrated using NOBIAS Chelate PA-1 resin. The dFe and dMn concentrated onto the resin were eluted with nitric acid and analyzed by a high-resolution ICP-MS (ELEMENT XR). Excitation-emission matrix fluorescence spectra for chromophoric dissolved organic matter (CDOM) in the samples were determined with a fluorescence spectrophotometer (FP-8500) to study metal-DOM interactions. Data of macronutrients, oxygen isotope ratios of water, and salinity were also used to identify source waters. The tracer N* (N*=0.87[nitrate]−16[phosphate]+2.9) of sediment resuspension on the continental shelf was calculated from macronutrient data.
Property of surface waters in the eastern region of ESAS (150−180°E) differed significantly from the western region (125−150°E). Nutrient-rich Pacific-sourced water existed in the eastern region, with a high dMn concentration (~70 nmol kg−1). The Pacific-sourced water was also characterized as having low-N*, resulting from a large sedimentary flux that releases dMn on the continental shelf. The dFe could have been released on the shelf as well, but the dFe remained low (~0.4 nmol kg−1) in the Pacific-sourced water. This is likely because dFe was more rapidly re-precipitated than dMn. In contrast to the eastern region, nutrient-poor Atlantic-sourced water existed in the western region. A positive correlation between the fraction of meteoric water (river water and precipitation), dFe, and humic-like CDOM in the Atlantic-sourced water confirmed a common freshwater source for dFe and DOM. Terrigenous organic ligands likely stabilized Fe in the dissolved phase, which was not the case with Mn. The fraction of sea-ice meltwater did not correlate to dFe and dMn in the Pacific- and Atlantic-sourced water. This result indicates that major factors controlling these metal concentrations in the ESAS may not be attributable to sea ice melt.
Observation in the ESAS was carried out in cooperation with the Nansen and Amundsen Basins Observational System (NABOS) expedition in September−October 2021. Surface water samples were collected at a depth of approximately 10 m using a peristaltic pump. Dissolved Fe (dFe) and Mn (dMn) in the samples were pre-concentrated using NOBIAS Chelate PA-1 resin. The dFe and dMn concentrated onto the resin were eluted with nitric acid and analyzed by a high-resolution ICP-MS (ELEMENT XR). Excitation-emission matrix fluorescence spectra for chromophoric dissolved organic matter (CDOM) in the samples were determined with a fluorescence spectrophotometer (FP-8500) to study metal-DOM interactions. Data of macronutrients, oxygen isotope ratios of water, and salinity were also used to identify source waters. The tracer N* (N*=0.87[nitrate]−16[phosphate]+2.9) of sediment resuspension on the continental shelf was calculated from macronutrient data.
Property of surface waters in the eastern region of ESAS (150−180°E) differed significantly from the western region (125−150°E). Nutrient-rich Pacific-sourced water existed in the eastern region, with a high dMn concentration (~70 nmol kg−1). The Pacific-sourced water was also characterized as having low-N*, resulting from a large sedimentary flux that releases dMn on the continental shelf. The dFe could have been released on the shelf as well, but the dFe remained low (~0.4 nmol kg−1) in the Pacific-sourced water. This is likely because dFe was more rapidly re-precipitated than dMn. In contrast to the eastern region, nutrient-poor Atlantic-sourced water existed in the western region. A positive correlation between the fraction of meteoric water (river water and precipitation), dFe, and humic-like CDOM in the Atlantic-sourced water confirmed a common freshwater source for dFe and DOM. Terrigenous organic ligands likely stabilized Fe in the dissolved phase, which was not the case with Mn. The fraction of sea-ice meltwater did not correlate to dFe and dMn in the Pacific- and Atlantic-sourced water. This result indicates that major factors controlling these metal concentrations in the ESAS may not be attributable to sea ice melt.