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向沿海地区迁移的影响


格陵兰冰盖质量的加速流失导致冰川退缩，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，峡湾沉积物在调节冰川环境向海洋生态系统供应硅方面的作用仍然受到很好的限制，特别是对于从沉积物到高纬度峡湾系统中上覆水域的硅通量的量化。在这项研究中，我们利用了从格陵兰岛西南部边缘的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（如冰川衍生的无定形二氧化硅）来解决这一知识差距。我们将下核观测与堆芯孵化和同位素质量平衡方法相结合，以评估溶解硅的底栖通量，并在早期成岩作用期间对这种通量的潜在贡献进行反卷积。我们的结果表明，分子扩散仅占底栖溶解硅传输的一部分。相对于周围的大陆架和高产的开阔海水域，我们站点估计的底栖溶解硅通量较小，这支持了峡湾在高纬度系统中作为活性硅的“陷阱”的作用。