Global Contrasts Between Oceanic Cycling of Cadmium and Phosphate
Global Contrasts Between Oceanic Cycling of Cadmium and Phosphate
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DOI：
10.1029/2021gb006952
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发表时间：
2021-06
影响因子：
5.2
通讯作者：
S. Roshan;T. DeVries
中科院分区：
文献类型：
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作者：
S. Roshan;T. DeVries
镉（Cd）是一种微量金属，其在海洋中的分布与营养物磷酸盐（PO43−）有显著的相似之处。这种相似性导致在古海洋学应用中使用Cd作为海洋营养循环的代表，但控制现代海洋中Cd循环的过程仍不清楚。在这项研究中，我们使用先前发表的Cd观测和人工神经网络来产生溶解Cd气候学，再现了观测到的Cd和PO43−分布之间的细微偏差。我们利用Cd和PO43−气候学，以及海洋环流逆模型来诊断溶解Cd和PO43−的生物地球化学源和汇。我们的计算表明，溶解的Cd和PO43−一样，在海洋表面被去除，并在地下有一个来源，这与Cd和PO43−同时进入下沉的有机颗粒相一致。然而，溶解Cd和PO43−的循环也存在差异。特别是，Cd:PO43−表面输出比在纬度上变化8倍，在铁受限的亚南极南大洋达到最高值。相对于PO43−，这消耗了低纬度温跃层中的Cd，同时通过富Cd颗粒的再生将多余的Cd添加到深水中。Cd在深海的再生比PO43−的再生深度略深，Cd:PO43−的再生比在700 ~ 1500 m处达到最大值。这些对比是造成Cd - PO43−关系轻微凹陷的原因，在解释古海洋学Cd记录时应予以考虑。
Cadmium (Cd) is a trace metal whose distribution in the ocean bears a remarkable resemblance to the nutrient phosphate (PO43−). This resemblance has led to the use of Cd as a proxy for ocean nutrient cycling in paleoceanographic applications, but the processes governing the cycling of Cd in the modern ocean remain unclear. In this study, we use previously published Cd observations and an Artificial Neural Network to produce a dissolved Cd climatology that reproduces the observed subtle deviations between the Cd and PO43− distributions. We use the Cd and PO43− climatologies, along with an ocean circulation inverse model, to diagnose the biogeochemical sources and sinks of dissolved Cd and PO43− . Our calculations reveal that dissolved Cd, like PO43− , is removed in the surface ocean and has a source in the subsurface, consistent with the simultaneous incorporation of Cd and PO43− into sinking organic particles. However, there are also contrasts between the cycling of dissolved Cd and PO43−. In particular, the Cd:PO43− surface export ratio varies 8‐fold across latitudes, reaching highest values in the iron‐limited sub‐Antarctic Southern Ocean. This depletes Cd relative to PO43− in the low‐latitude thermocline while adding excess Cd to deep waters by the regeneration of Cd‐enriched particles. Also, Cd tends to regenerate slightly deeper than PO43− in the subsurface ocean, and the Cd:PO43− regeneration ratio reaches a maximum at 700–1,500 m. These contrasts are responsible for a slight concavity in the Cd‐PO43− relationship and should be considered when interpreting paleoceanographic Cd records.