Annually Resolved Propagation of CFCs and SF 6 in the Global Ocean Over Eight Decades
Annually Resolved Propagation of CFCs and SF 6 in the Global Ocean Over Eight Decades
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八年来每年解决全球海洋中 CFC 和 SF 6 的扩散问题
DOI：
10.1029/2022jc019337
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发表时间：
2023
期刊：
影响因子：
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通讯作者：
Smethie, William M.
中科院分区：
文献类型：
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作者：
Cimoli, Laura;Gebbie, Geoffrey;Purkey, Sarah G.;Smethie, William M.
海洋瞬态示踪剂，如氯氟烃（CFCs）和六氟化硫（SF6），跟踪海洋内部中层至深海水体的传播。然而，它们在时间和空间上的稀疏性限制了它们在量化全球海洋环流及其十年变率方面的效用。本文提出的时间修正法（TCM）是一种利用现有CFCs和SF6观测数据求解描述海洋表面至海洋内部稳态输运的绿色函数（GF）的新方法。从GF，我们重建全球示踪剂浓度（和相关的不确定性）在海洋内部的年度分辨率（1940年至2021年）。空间分辨率包括跨越沿着世界海洋环流实验/全球海洋船基水文调查计划线的水柱的50个中性密度水平。重建的示踪剂浓度返回了CFC和SF6扩散到内陆海洋新区域（例如西北太平洋深处）的全球视图。例如，它们捕捉到了不同的北大西洋深水成分向南扩散和赤道再循环，以及富含CFC的南极底层水从南大洋扩散到北太平洋、东印度洋和西大西洋。重建的示踪剂浓度在大多数位置（约75%）符合数据，表明稳态循环在大多数情况下都成立。重建和观察到的浓度之间的差异提供了深入了解通风率的变化在十年的时间尺度。作为一个例子，我们推断了亚极地模式水（SAMW）的年代际变化，并发现从1992年到2014年SAMW通风量增加，突出了TCM利用稀疏示踪剂观测的技能。
Oceanic transient tracers, such as chlorofluorocarbons (CFCs) and sulfur‐hexafluoride (SF6), trace the propagation of intermediate‐to‐abyssal water masses in the ocean interior. Their temporal and spatial sparsity, however, has limited their utility in quantifying the global ocean circulation and its decadal variability. TheTime‐Correction Method(TCM) presented here is a new approach to leverage the available CFCs and SF6observations to solve for the Green's functions (GFs) describing the steady‐state transport from the surface to the ocean interior. From the GFs, we reconstruct global tracer concentrations (and associated uncertainties) in the ocean interior at annual resolution (1940–2021). The spatial resolution includes 50 neutral density levels that span the water column along World Ocean Circulation Experiment/Global Ocean Ship‐Based Hydrographic Investigations Program lines. The reconstructed tracer concentrations return a global view of CFCs and SF6spreading into new regions of the interior ocean, such as the deep north‐western Pacific. For example, they capture the southward spreading and equatorial recirculation of distinct North Atlantic Deep Water components, and the spreading of CFC‐rich Antarctic Bottom Water out of the Southern Ocean and into the North Pacific, East Indian, and West Atlantic. The reconstructed tracer concentrations fit the data in most locations (∼75%), indicating that a steady‐state circulation holds for the most part. Discrepancies between the reconstructed and observed concentrations offer insight into ventilation rate changes on decadal timescales. As an example, we infer decadal changes in Subantartic Mode Water (SAMW) and find an increase in SAMW ventilation from 1992 to 2014, highlighting the skill of the TCM in leveraging the sparse tracer observations.