Aluminum (Al) is delivered to surface ocean waters by aeolian dust, making it a promising tracer to constrain dust deposition rates and the atmospheric supply of trace metal micronutrients. Over recent years, dissolved Al has been mapped along the GEOTRACES transects, providing unparalleled coverage of the world ocean. However, inferring atmospheric input rates from these observations is complicated by a suite of additional processes that influence the Al distribution, including reversible particle scavenging, biological uptake by diatoms, hydrothermal sources, sediment resuspension. Here we employ a data-assimilation model of the oceanic Al cycle that explicitly accounts for these processes, allowing the atmospheric signal to be extracted. We conduct an ensemble of model optimizations that test different dust deposition distributions and consider spatial variations in Al solubility, thereby inferring the atmospheric Al supply that is most consistent with GEOTRACES observations. We find that 37.2 ± 11.0 Gmol/yr of soluble Al is added to the global ocean, dominated in the Atlantic Ocean, and that Al fractional solubility varies strongly as a function of atmospheric dust concentration. Our model also suggests that 6.1 ± 2.4 Gmol Al/yr is injected from hydrothermal vents, and that vertical Al redistribution through the water column is dominated by abiotic reversible scavenging rather than uptake by diatoms. Our results have important implications for the oceanic iron (Fe) budget: based on the soluble Fe:Al ratio of dust, we infer that aeolian Fe inputs lie between 3.82 and 9.25 Gmol/yr globally, and fall short of the biological Fe demand in most ocean regions.

中文翻译：

---

受海洋铝循环数据同化模型约束的海洋尘埃沉积率

铝 (Al) 由风尘输送到地表海水，使其成为限制灰尘沉积率和大气中痕量金属微量营养素供应的有希望的示踪剂。近年来，已沿 GEOTRACES 横断面绘制了溶解铝，提供了无与伦比的世界海洋覆盖范围。然而，从这些观测中推断大气输入速率会受到一系列影响铝分布的额外过程的影响，包括可逆的粒子清除、硅藻的生物吸收、热液源、沉积物再悬浮。在这里，我们采用了海洋铝循环的数据同化模型，该模型明确解释了这些过程，从而可以提取大气信号。我们进行了一系列模型优化，测试不同的尘埃沉积分布并考虑铝溶解度的空间变化，从而推断与 GEOTRACES 观测最一致的大气铝供应。我们发现 37.2 ± 11.0 Gmol/yr 的可溶性铝被添加到全球海洋中，在大西洋中占主导地位，并且铝的分数溶解度作为大气尘埃浓度的函数变化很大。我们的模型还表明，6.1 ± 2.4 Gmol Al/yr 从热液喷口注入，并且通过水柱的垂直铝重新分布主要由非生物可逆清除而不是硅藻吸收。我们的结果对海洋铁 (Fe) 收支具有重要意义：基于尘埃的可溶性 Fe:Al 比率，我们推断风成 Fe 输入介于 3.82 和 9 之间。