The Amundsen Sea Polynya (ASP) is the most biologically productive area around Antarctica due to the input of iron-rich glacial meltwater (GMW). However, the source and path of GMW in the ASP, and how these have changed since the Dotson Ice Shelf (DIS), a primary GMW supplier, began experiencing a cooling period after 2011, remain unclear. This study presents the distribution of GMW in the ASP during the austral summer of 2020. Subsurface GMW proportions were estimated using a composite tracer derived from potential temperature, salinity, and dissolved oxygen, while surface GMW were using 226Ra and 228Ra. The results indicate that GMW in the ASP originates from DIS and Pine Island Bay. Surface GMW upwelled from the melting basal cavity of DIS is transported northwestward by katabatic winds, while subsurface GMW is transported northwestward beneath the mixed layer, with the upper portion upwelling to the surface in the ASP center along isopycnals (σθ) of 27.40 to 27.45 kg/m3. Depth variations of these isopycnals correlate well with brine inventories released by winter sea ice formation, suggesting that sea ice formation influences seawater σθ structures and consequently the transport path of subsurface GMW. Compared to 2011, the GMW content in the ASP in 2020 decreased by nearly half, and the transport routes have also changed. These changes align with the significantly reduced GMW discharge from the DIS after 2012. Our study confirms that the GMW system in the ASP has undergone significant changes following the onset of the cooling period experienced by the DIS.

中文翻译：

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以镭和氧同位素说明的阿蒙森海冰间湖周围冰川融水系统的变化


阿蒙森海冰间湖 （ASP） 是南极洲周围生物生产力最高的地区，因为含有富含铁的冰川融水 （GMW）。然而，目前尚不清楚 GMW 在 ASP 中的来源和路径，以及自 2011 年主要 GMW 供应商多特森冰架 （DIS） 开始经历冷却期以来这些变化如何。本研究介绍了 2020 年南夏季 GMW 在 ASP 中的分布。使用来自潜在温度、盐度和溶解氧的复合示踪剂估计地下 GMW 比例，而表面 GMW 使用 226Ra 和 228Ra。结果表明，ASP 中的 GMW 来源于 DIS 和 Pine Island Bay。从 DIS 熔化基腔上升流的表面 GMW 被下坡风向西北输送，而地下 GMW 在混合层下方向西北输送，上部沿 27.40 至 27.45 kg/m3 的等密度 （σθ） 上升流到 ASP 中心的表面。这些等密度的深度变化与冬季海冰形成释放的盐水库存密切相关，表明海冰的形成会影响海水 σθ 结构，从而影响地下 GMW 的传输路径。与 2011 年相比，2020 年 ASP 中的 GMW 含量下降了近一半，运输路线也发生了变化。这些变化与 2012 年后 DIS 显着减少的 GMW 排放相一致。我们的研究证实，在 DIS 经历的冷却期开始后，ASP 中的 GMW 系统发生了重大变化。