Supra‐permafrost submarine groundwater discharge (SGD) in the Arctic is potentially important for coastal biogeochemistry and will likely increase over the coming decades owing to climate change. Despite this, land‐to‐ocean material fluxes via SGD in Arctic environments have seldom been quantified. This study used radium (Ra) isotopes to quantify SGD fluxes to an Arctic coastal lagoon (Simpson Lagoon, Alaska) during five sampling periods between 2021 and 2023. Using a Ra mass balance model, we found that the SGD water flux was substantial and dependent on environmental conditions. No measurable SGD was detected during the spring sampling period (June 2022), when the lagoon was partially ice‐covered. During ice‐free periods, the main driver of SGD in this location is wind‐driven lagoon water level changes, not tides, which control surface water recirculation through sediments along the lagoon boundary. A combination of wind strength and direction led to low SGD fluxes in July 2022, with an SGD flux of (6 ± 3) × 106 m3 d−1, moderate fluxes in August 2021 and July 2023, which had an average flux of (17 ± 9) × 106 m3 d−1, and high fluxes in October 2022, at (79 ± 16) × 106 m3 d−1. This work demonstrates how soil and environmental conditions in the Arctic impact Ra mobilization, laying a foundation for future SGD studies in the Arctic and shedding light on the major processes driving Ra fluxes in this important environment.

中文翻译：

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北极沿海泻湖海底地下水排放的季节性

北极的超永久冻土海底地下水排放（SGD）对于沿海生物地球化学具有潜在的重要意义，并且由于气候变化，未来几十年可能会增加。尽管如此，北极环境中通过 SGD 从陆地到海洋的物质通量很少被量化。本研究使用镭 (Ra) 同位素来量化 2021 年至 2023 年间五个采样周期内流入北极沿海泻湖（阿拉斯加辛普森泻湖）的 SGD 通量。使用 Ra 质量平衡模型，我们发现 SGD 水通量是巨大且依赖的关于环境条件。在春季采样期间（2022 年 6 月），当泻湖部分被冰覆盖时，没有检测到可测量的 SGD。在无冰期，该地区 SGD 的主要驱动因素是风驱动的泻湖水位变化，而不是潮汐，潮汐通过泻湖边界的沉积物控制地表水再循环。风力和风向的共同作用导致 2022 年 7 月 SGD 通量较低，SGD 通量为 (6 ± 3) × 106米3d−1，2021年8月和2023年7月的通量中等，平均通量为(17±9)×106米3d−1，以及 2022 年 10 月的高通量，为 (79 ± 16) × 106米3d−1。这项工作展示了北极的土壤和环境条件如何影响 Ra 动员，为未来北极的 SGD 研究奠定了基础，并揭示了在这个重要环境中驱动 Ra 通量的主要过程。