Insights into the origins, molecular characteristics and distribution of iron-binding ligands in the Arctic Ocean

Williford, Tatiana; Amon, Rainer M. W.; Benner, Ronald; Kaiser, Karl; Bauch, Dorothea; Stedmon, Colin A.; Yan, Guoxin; Walker, Sally A.; Loeff, Michiel Rutgers v. d.; Klunder, Maarten B

doi:10.1016/j.marchem.2021.103936

Cited by 14 publications

(35 citation statements)

References 85 publications

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“…The winter mixed layer depth is apparent at around 100 m below which there are coincident thermo-, halo-and DOMclines. In this profile the winter mixed layer is capped by a surface lens with temperatures above freezing for its given salinity (Figure 4d, note deviation from freezing at salinity ∼34), and reduced salinity (S p < 34.35) and DOM fluorescence that has decreased from 0.010 to 0.004 nm −1 (Figure 4e) consistent with previous studies (Granskog, Pavlov, et al, 2015;Williford et al, 2021). This likely reflects the addition of summer seaice melt water (Bauch et al, 2011;Paffrath et al, 2021) into the surface layer.…”

Section: Resultssupporting

confidence: 89%

“…In addition, multi‐channel in situ fluorometers would be able to better differentiate between Arctic DOM sources as they differ in their spectral properties (Gonçalves‐Araujo et al., 2016; Makarewicz et al., 2018), while spectral absorption sensors such as those used for nitrate can potentially provide high resolution estimates of DOC (Gonçalves‐Araujo et al., 2020). Surface DOM measurements can easily distinguish the frontal regions on either side of the TPD, and in the vertical provides a powerful tool to guide water sampling of other tracers in the water column (Charette et al., 2020; Williford et al., 2021). This offers a valuable and currently underutilized additional tracer for deciphering Arctic circulation and freshwater distribution.…”

Section: Discussionmentioning

confidence: 99%

“…As such the relative contributions of waters from the Siberian shelf (Atlantic origin) and Chukchi shelf (Pacific) can vary (Anderson et al., 2004). The TPD carries a clear terrigenous/riverine signal from the Siberian shelves across the Arctic and onwards to the North Atlantic (Anderson et al., 2004; Charette et al., 2020; Williford et al., 2021), but can also entrain a Pacific Water and East Siberian shelf signal, most noticeable as a lack of nitrate and excess silicate (Anderson et al., 2013; Bauch et al., 2011; Jones & Anderson, 1986; McLaughlin et al., 2004), or by having distinctly different DOM properties (Amon et al, 2003; Gonçalves‐Araujo et al., 2016; Stedmon, Amon, et al., 2011; Williford et al., 2021). These geochemical signals can therefore be used as a tracers of water origin and circulation in the Arctic Ocean.…”

Section: Introductionmentioning

confidence: 99%

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Insights Into Water Mass Origins in the Central Arctic Ocean From In‐Situ Dissolved Organic Matter Fluorescence

et al. 2021

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The Arctic Ocean receives a large supply of dissolved organic matter (DOM) from its catchment and shelf sediments, which can be traced across much of the basin's upper waters. This signature can potentially be used as a tracer. On the shelf, the combination of river discharge and sea‐ice formation, modifies water densities and mixing considerably. These waters are a source of the halocline layer that covers much of the Arctic Ocean, but also contain elevated levels of DOM. Here we demonstrate how this can be used as a supplementary tracer and contribute to evaluating ocean circulation in the Arctic. A fraction of the organic compounds that DOM consists of fluoresce and can be measured using in‐situ fluorometers. When deployed on autonomous platforms these provide high temporal and spatial resolution measurements over long periods. The results of an analysis of data derived from several Ice Tethered Profilers (ITPs) offer a unique spatial coverage of the distribution of DOM in the surface 800 m below Arctic sea‐ice. Water mass analysis using temperature, salinity and DOM fluorescence, can clearly distinguish between the contribution of Siberian terrestrial DOM and marine DOM from the Chukchi shelf to the waters of the halocline. The findings offer a new approach to trace the distribution of Pacific waters and its export from the Arctic Ocean. Our results indicate the potential to extend the approach to separate freshwater contributions from, sea‐ice melt, riverine discharge and the Pacific Ocean.

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Section: Resultssupporting

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Insights Into Water Mass Origins in the Central Arctic Ocean From In‐Situ Dissolved Organic Matter Fluorescence

et al. 2021

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“…Fe and Mn, as well as Co, were released from the sediment, where it is known that the oxidation kinetics of DFe are much faster than of DMn (Stumm & Morgan, 1981;Millero et al, 1987) resulting in an initially much faster decrease of Fe in the dissolved phase. However, when DFe has decreased to the level that can be kept in solution by Fe binding organic ligands, the remaining Fe is stabilized (Slagter et al, 2017(Slagter et al, , 2019Thuróczy et al, 2011;Williford et al, 2021). The average lifetime of these ligands was established to be at least twice that of Fe in the Western Atlantic Ocean (Gerringa et al, 2015).…”

Section: The Influence Of the Tpdmentioning

confidence: 99%

“…Besides dirty sea ice, river water contains large amounts of humic material, which can bind or chelate trace metals, especially Fe, but also Mn, Zn, Cu, Co, Ni, and Cd that are known to bind to dissolved organic ligands. Humic material flocculates and sinks out of the water column to a significant degree in estuaries (Yang et al., 2017), but the fraction of humics that reaches the ocean, increases the solubility and thus the residence time of trace metals as predominantly studied for Fe and Cu (Laglera & van den Berg., 2009; Laglera et al., 2019; Sholkovitz & Copland, 1981; Slagter et al., 2019; Sukekava et al., 2018; Whitby & van den Berg, 2015; Williford et al., 2021; Yang et al., 2017). Although this is in general known for the exchange between rivers and oceans, there is substantial variation between different river systems and preciously little is known about the distribution of riverine metal input in the Arctic Ocean.…”

Section: Introductionmentioning

confidence: 99%

Dissolved Cd, Co, Cu, Fe, Mn, Ni, and Zn in the Arctic Ocean

et al. 2021

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During the Polarstern (PS94) expedition, summer 2015, part of the international GEOTRACES program, sources and sinks of dissolved (D) Cd, Co, Cu, Fe, Mn, Ni, and Zn were studied in the central Arctic Ocean. In the Polar Surface Water in which the TransPolar Drift (TPD) is situated, salinity and δ18O derived fractions indicated a distinct riverine source for silicate DCo, DCu, DFe, DMn, and DNi. Linear relationships between DMn and the meteoric fraction depended on source distance, likely due to Mn‐precipitation during transport. In the upper 50 m of the Makarov Basin, outside the TPD core, DCo, DMn, DNi, DCd, and DCu were enriched by Pacific waters, whereas DFe seemed diluted. DCo, DFe, DMn, and DZn were relatively high in the Barents Sea and led to enrichment of Atlantic water flowing into the Nansen Basin. Deep concentrations of all metals were significantly lower in the Makarov Basin compared to the Nansen and Amundsen, the Eurasian, Basins. The Gakkel ridge hydrothermal input and higher continental slope convection are explanations for higher metal concentrations in the Eurasian Basins. Although scavenging rates are lower in the Makarov Basin compared to the Eurasian Basins, the residence time is longer and therefore scavenging can decrease the dissolved concentrations with time. This study provides a baseline to assess future change, and additionally identifies processes driving trace metal distributions. Our results underline the importance of fluvial input as well as shelf sources and internal cycling, notably scavenging, for the distribution of bio‐active metals in the Arctic Ocean.

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Insights into Water Mass Origins in the Central Arctic Ocean from in-situ Dissolved Organic Matter Fluorescence.

Stedmon

Amon

Bauch

et al. 2021

Preprint

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The central Arctic Ocean is surrounded by expansive shelf seas which influence ocean circulation and seawater properties (Figure 1). Shallow depths restrict deep water exchange to only occur in the Fram Strait. Much of the surface water inflow occurs over the expansive shelf sea areas, where river runoff and extensive seasonal sea-ice formation and melt modify the physical and chemical properties. Inflowing waters from the Pacific and Atlantic also loose heat to the atmosphere and are cooled during their passage over the shelves (

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Insights into the origins, molecular characteristics and distribution of iron-binding ligands in the Arctic Ocean

Cited by 14 publications

References 85 publications

Insights Into Water Mass Origins in the Central Arctic Ocean From In‐Situ Dissolved Organic Matter Fluorescence

Insights Into Water Mass Origins in the Central Arctic Ocean From In‐Situ Dissolved Organic Matter Fluorescence

Dissolved Cd, Co, Cu, Fe, Mn, Ni, and Zn in the Arctic Ocean

Insights into Water Mass Origins in the Central Arctic Ocean from in-situ Dissolved Organic Matter Fluorescence.

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