Accelerated mass loss from the Greenland Ice Sheet leads to retreating glaciers and enhanced freshwater runoff to adjacent coastal regions, potentially providing additional essential nutrients, such as silicon, to downstream primary producers. However, the role of fjordic sediments in modulating the supply of silicon from glacial environments to marine ecosystems remains poorly constrained, particularly for the quantification of silicon fluxes from the sediments into overlying waters in high-latitude fjordic systems. In this study, we use the concentration and stable isotopic composition of dissolved silicon in pore waters and core-top waters, and amorphous silica phases (such as glacially-derived amorphous silica) in sediments and suspended particulate matter, collected from two fjords in the southwest Greenland margin to address this knowledge gap. We combine downcore observations with core incubations and isotope mass balance approaches to assess the benthic flux of dissolved silicon and deconvolve potential contributors to this flux during early diagenesis. Our results suggest that molecular diffusion only accounts for a portion of benthic dissolved silicon transport. Relative to surrounding continental shelves and highly-productive open ocean waters, the estimated benthic dissolved silicon flux at our sites is smaller in magnitude, supporting the role of fjords as a ‘trap’ for reactive silicon in high-latitude systems.

中文翻译：

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硅同位素揭示了峡湾过程对活性硅从冰川到沿海地区运输的影响


格陵兰冰盖的质量加速流失导致冰川后退，并增加流向邻近沿海地区的淡水径流，从而可能为下游初级生产者提供额外的必需营养物质，例如硅。然而，峡湾沉积物在调节从冰川环境到海洋生态系统的硅供应方面的作用仍然受到很少的限制，特别是对于高纬度峡湾系统中从沉积物到上覆水域的硅通量的量化。在这项研究中，我们使用了从两个峡湾收集的孔隙水和岩心顶部水中溶解硅的浓度和稳定同位素组成，以及沉积物和悬浮颗粒物中的无定形二氧化硅相（例如冰川衍生的无定形二氧化硅）。格陵兰岛西南边缘旨在解决这一知识差距。我们将岩心观察与岩心孵化和同位素质量平衡方法结合起来，评估溶解硅的底栖通量，并对早期成岩过程中对该通量的潜在贡献者进行反卷积。我们的结果表明分子扩散仅占底栖溶解硅运输的一部分。相对于周围的大陆架和高产的开放海洋水域，我们所在地的估计海底溶解硅通量较小，这支持了峡湾作为高纬度系统中活性硅“陷阱”的作用。