Hopwood Mark J, Carroll Dustin, Gu Yuanyuan, Huang Xin, Krause Jana, Cozzi Stefano, Cantoni Carolina, Gastelu Barcena María Fernanda, Carroll Shandy, Körtzinger Arne
Department of Ocean Science and Engineering Southern University of Science and Technology Shenzhen China.
Moss Landing Marine Laboratories San José State University Moss Landing CA USA.
Global Biogeochem Cycles. 2025 Jan;39(1):e2023GB008080. doi: 10.1029/2023GB008080. Epub 2025 Jan 1.
Discharge of calved ice, runoff and mixing driven by subglacial discharge plumes likely have consequences for marine biogeochemistry in Disko Bay, which hosts the largest glacier in the northern hemisphere, Sermeq Kujalleq. Glacier retreat and increasing runoff may impact the marine silica cycle because glaciers deliver elevated concentrations of dissolved silica (dSi) compared to other macronutrients. However, the annual flux of dSi delivered to the ocean from the Greenland Ice Sheet is poorly constrained because of difficulties distinguishing the overlapping influence of different dSi sources. Here we constrain silica dynamics around Disko Bay, including the Ilulissat Icefjord and four other regions receiving glacier runoff with contrasting levels of productivity and turbidity. Both dissolved silica and Si* ([dSi]-[NO ]) concentrations indicated conservative dynamics in two fjords with runoff from land-terminating glaciers, consistent with the results of mixing experiments. In three fjords with marine-terminating glaciers, macronutrient-salinity distributions were strongly affected by entrainment of nutrients in subglacial discharge plumes. Entrainment of dSi from saline waters explained 93 ± 51% of the dSi enrichment in the outflowing plume from Ilulissat Icefjord, whereas the direct contribution of freshwater to dSi in the plume was likely 0%-3%. Whilst not distinguished herein, other minor regional dSi sources include icebergs and dissolution of amorphous silica (aSi) in either pelagic or benthic environments. Our results suggest that runoff around Greenland is supplemented as a dSi source by minor fluxes of 0.25 ± 0.67 Gmol yr dSi from icebergs and ∼1.9 Gmol year from pelagic aSi dissolution.
由冰下排放羽流驱动的崩解冰、径流和混合过程可能会对迪斯科湾的海洋生物地球化学产生影响，迪斯科湾拥有北半球最大的冰川—— Sermeq Kujalleq。冰川消退和径流增加可能会影响海洋硅循环，因为与其他大量营养素相比，冰川输送的溶解硅（dSi）浓度更高。然而，由于难以区分不同dSi来源的重叠影响，格陵兰冰盖向海洋输送的dSi年通量受到的限制很大。在这里，我们研究了迪斯科湾周围的硅动力学，包括伊卢利萨特冰峡湾和其他四个接收冰川径流的区域，这些区域的生产力和浊度水平各不相同。溶解硅和Si*（[dSi]-[NO]）浓度表明，在两条有来自陆地末端冰川径流的峡湾中，硅的动态变化是保守的，这与混合实验的结果一致。在三条有海洋末端冰川的峡湾中，大量营养素-盐度分布受到冰下排放羽流中营养物质夹带的强烈影响。来自盐水的dSi夹带解释了伊卢利萨特冰峡湾流出羽流中dSi富集的93±51%，而淡水对羽流中dSi的直接贡献可能为0%-3%。虽然本文未区分其他较小的区域dSi来源，但包括冰山以及上层或底层环境中无定形硅（aSi）的溶解。我们的结果表明，格陵兰周围的径流作为dSi来源得到了补充，来自冰山的dSi通量为0.25±0.67 Gmol yr，来自上层aSi溶解的通量约为1.9 Gmol yr。
