Abstract Recent studies suggest that seafloor hydrothermal vents could be an important source of iron (Fe) to the surface ocean, stimulating plankton growth and biological carbon export. However, quantifying the supply of hydrothermal Fe to the surface ocean requires accurately modeling its stabilization and removal processes, which are poorly known. Here, we determine the physical speciation of dissolved Fe along an oceanographic transect following a coherent hydrothermal plume that emanates from the East Pacific Rise (EPR) and persists westward over 4,000 km in the Tropical South Pacific. Our observations show that the plume persists horizontally, but descends vertically, and consists primarily of very large Fe colloids. Guided by these observations, we develop a new size-resolved mechanistic model of hydrothermal Fe dispersion in this region, in which the stabilization of hydrothermal Fe is explained by a reversible particulate exchange process. This model accurately captures the lateral dispersion, downward settling and physical speciation of hydrothermal Fe along this transect. An alternate model that uses a hydrothermal source of Fe-binding ligands to facilitate Fe transport within the deep ocean can reproduce the long-range transport of hydrothermal Fe, but does not reproduce the vertical descent of the plume. Our model shows that hydrothermal Fe vented from the EPR is trapped in the deep ocean, and only 1% of this iron ever makes it to the surface where it can stimulate biological productivity. At the global scale, 3-5% of hydrothermal Fe makes it to the surface ocean, the vast majority of which originates from Southern Ocean vents and upwells in the Southern Ocean. Our best estimate of the global supply of hydrothermal Fe to the surface ocean, based on data-constrained estimates of ocean circulation, mantle 3He venting, and the hydrothermal Fe:3He ratio from the EPR, is 0.12 ± 0.07 Gmol yr−1. This is about 60-70 times lower than the supply of Fe from aerosol dust deposition, but could be regionally important in the Antarctic zone of the Southern Ocean.

中文翻译：

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可逆清除捕获深海中的热液铁

摘要 最近的研究表明，海底热液喷口可能是表层海洋铁 (Fe) 的重要来源，刺激浮游生物生长和生物碳输出。然而，量化地表海洋热液铁的供应需要对其稳定和去除过程进行准确建模，而这些过程鲜为人知。在这里，我们确定了沿着海洋学断面溶解铁的物理形态，该热液从东太平洋隆起 (EPR) 发出并在热带南太平洋向西持续超过 4,000 公里。我们的观察表明，羽流水平持续存在，但垂直下降，主要由非常大的 Fe 胶体组成。在这些观察的指导下，我们开发了该区域热液铁扩散的新的尺寸分辨机制模型，其中热液铁的稳定是通过可逆的颗粒交换过程来解释的。该模型准确地捕获了沿该断面的热液铁的横向扩散、向下沉降和物理形态。使用铁结合配体的热液源促进深海内铁传输的替代模型可以重现热液铁的远程传输，但不能重现羽流的垂直下降。我们的模型表明，从 EPR 排出的热液 Fe 被困在深海中，并且只有 1% 的这种铁会浮出水面，在那里它可以刺激生物生产力。在全球范围内，3-5% 的热液铁进入表层海洋，其中绝大多数来自南大洋的喷口和南大洋的上升流。根据对海洋环流、地幔 3He 排放和来自 EPR 的热液 Fe:3He 比率的数据约束估计，我们对全球地表海洋热液铁供应的最佳估计为 0.12 ± 0.07 Gmol yr−1。这比气溶胶尘埃沉积产生的铁供应量低约 60-70 倍，但在南大洋的南极地区可能具有重要的区域意义。