Table1_Trace Element (Fe, Co, Ni and Cu) Dynamics Across the Salinity Gradient in Arctic and Antarctic Glacier Fjords.XLS

Around the Greenlandic and Antarctic coastlines, sediment plumes associated with glaciers are significant sources of lithogenic material to the ocean. These plumes contain elevated concentrations of a range of trace metals, especially in particle bound phases, but it is not clear how these particles affect dissolved (<0.2 µm) metal distributions in the ocean. Here we show, using transects in 8 glacier fjords, trends in the distribution of dissolved iron, cobalt, nickel and copper (dFe, dCo, dNi, dCu). Following rapid dFe loss close to glacier outflows, dFe concentrations in particular showed strong similarities between different fjords. Similar dFe concentrations were also observed between seasons/years when Nuup Kangerlua (SW Greenland) was revisited in spring, mid- and late-summer. Dissolved Cu, dCo and dNi concentrations were more variable and showed different gradients with salinity depending on the fjord, season and year. The lack of consistent trends for dCu and dNi largely reflects less pronounced differences contrasting the concentration of inflowing shelf waters with fresher glacially-modified waters. Particles also made only small contributions to total dissolvable Cu (dCu constituted 83 ± 28% of total dissolvable Cu) and Ni (dNi constituted 86 ± 28% of total dissolvable Ni) within glacier plumes. For comparison, dFe was a lower fraction of total dissolvable Fe; 3.5 ± 4.8%. High concentrations of total dissolvable Fe in some inner-fjord environments, up to 77 µM in Ameralik (SW Greenland), may drive enhanced removal of scavenged type elements, such as Co. Further variability may have been driven by local bedrock mineralogy, which could explain high concentrations of dNi (25–29 nM) and dCo (6–7 nM) in one coastal region of west Greenland (Kangaatsiaq). Our results suggest that dissolved trace element distributions in glacier fjords are influenced by a range of factors including: freshwater concentrations, local geology, drawdown by scavenging and primary production, saline inflow, and sediment dynamics. Considering the lack of apparent seasonality in dFe concentrations, we suggest that fluxes of some trace elements may scale proportionately to fjord overturning rather than directly to freshwater discharge flux.

在格陵兰岛与南极洲沿岸海域，与冰川相关的沉积物羽流是海洋陆源物质的重要来源。这类羽流中多种痕量金属的浓度显著升高，尤以颗粒结合态为主，但目前尚不清楚这些颗粒物如何影响海洋中溶解态（<0.2微米）金属的分布格局。本研究通过对8条冰川峡湾的断面采样，揭示了溶解态铁（dissolved iron, dFe）、溶解态钴（dissolved cobalt, dCo）、溶解态镍（dissolved nickel, dNi）与溶解态铜（dissolved copper, dCu）的分布趋势。在冰川出口附近区域，溶解态铁会快速损耗，而不同峡湾中的溶解态铁浓度整体呈现出高度相似的变化特征。在春季、夏季中晚期对格陵兰岛西南部的努普康格鲁阿（Nuup Kangerlua）海域进行重采样时，也观测到了相似的溶解态铁浓度水平。溶解态铜、钴与镍的浓度则表现出更强的变异性，且其随盐度的变化梯度因峡湾、季节与年份的不同而存在显著差异。溶解态铜与镍未呈现统一变化趋势，这在很大程度上反映了：流入的陆架水与更淡的冰川改造水之间的浓度差异并不显著。在冰川羽流中，颗粒物对总可溶态铜（溶解态铜占总可溶态铜的83±28%）与镍（溶解态镍占总可溶态镍的86±28%）的贡献仅占较小比例。相比之下，溶解态铁仅占总可溶态铁的极小比例，仅为3.5±4.8%。部分峡湾内湾区域的总可溶态铁浓度极高，在格陵兰岛西南部的阿梅拉利克（Ameralik）海域甚至可达77微摩尔，这可能会促进钴等清除型元素的沉降清除过程。进一步的浓度变异性可能由当地基岩矿物组成所驱动，这也可以解释格陵兰岛西部沿海区域康加茨亚克（Kangaatsiaq）海域中溶解态镍（25~29纳摩尔）与钴（6~7纳摩尔）的高浓度现象。本研究结果表明，冰川峡湾中的溶解态痕量元素分布格局受多种因素共同调控，包括：淡水浓度、本地地质条件、清除作用与初级生产导致的元素损耗、高盐度水流入侵以及沉积物动力学过程。鉴于溶解态铁浓度未表现出明显的季节周期性，我们推测部分痕量元素的通量可能与峡湾翻转环流强度呈比例关系，而非直接与淡水排放通量相关。