Perspectives of transient tracer applications and limiting cases
Perspectives of transient tracer applications and limiting cases
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DOI：
10.5194/os-11-699-2015
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发表时间：
2015-01-01
期刊：
影响因子：
3.2
通讯作者：
Bullister, J. L.
中科院分区：
文献类型：
--
作者：
Stoeven, T.;Tanhua, T.;Bullister, J. L.
目前可用的瞬态示踪剂有不同的应用范围，这些范围是由它们的时间输入（时间顺序瞬态示踪剂）或衰变速率（放射性瞬态示踪剂）定义的。瞬态示踪剂的范围从用于高度通风水体的示踪剂，如六氟化硫（SF6）、氚（H-3）和氯氟化碳（CFCs），到用于通风较差的深海盆地的示踪剂，如氩-39 （Ar-39）和放射性碳（C-14）。在这种情况下，高度通风的水团被定义为在过去十年中与大气接触的水团。瞬态示踪剂可用于经验地约束传输时间分布（TTD），该分布通常可以近似为逆高斯分布（IG）。IG-TTD提供了关于通风和水包的平流/扩散特性的信息。本文介绍了常用的瞬态示踪剂对，并利用有效性域的新概念对IG-TTD的应用范围进行了概述。利用南大西洋和南大洋三次不同巡航的CFC-12、CFC-11和SF6数据，以及20世纪80年代和90年代初东大西洋和威德尔海的Ar-39数据来证明这种方法。我们发现，igg - ttd可以沿格林尼治子午线南向46°S被约束，对应于亚南极锋（SAF）表示应用极限。南极中间水（AAIW）描述了垂直方向上的极限水层。平流分量和扩散分量比值的显著高低，与其说是描述了水包的物理性质，不如说是描述了IG-TTD模型的有效区域与应用极限之间的过渡。Ar-39和CFC数据的结合对SAF北部深水中的IG-TTD施加了限制，但没有超出这个限制。
Currently available transient tracers have different application ranges that are defined by their temporal input (chronological transient tracers) or their decay rate (radioactive transient tracers). Transient tracers range from tracers for highly ventilated water masses such as sulfur hexafluoride (SF6) through tritium (H-3) and chlorofluorocarbons (CFCs) up to tracers for less ventilated deep ocean basins such as argon-39 (Ar-39) and radiocarbon (C-14). In this context, highly ventilated water masses are defined as water masses that have been in contact with the atmosphere during the last decade. Transient tracers can be used to empirically constrain the transit time distribution (TTD), which can often be approximated with an inverse Gaussian (IG) distribution. The IG-TTD provides information about ventilation and the advective/diffusive characteristics of a water parcel. Here we provide an overview of commonly used transient tracer couples and the corresponding application range of the IG-TTD by using the new concept of validity areas. CFC-12, CFC-11 and SF6 data from three different cruises in the South Atlantic Ocean and Southern Ocean as well as Ar-39 data from the 1980s and early 1990s in the eastern Atlantic Ocean and the Weddell Sea are used to demonstrate this method. We found that the IG-TTD can be constrained along the Greenwich Meridian south to 46 degrees S, which corresponds to the Subantarctic Front (SAF) denoting the application limit. The Antarctic Intermediate Water (AAIW) describes the limiting water layer in the vertical. Conspicuous high or lower ratios between the advective and diffusive components describe the transition between the validity area and the application limit of the IG-TTD model rather than describing the physical properties of the water parcel. The combination of Ar-39 and CFC data places constraints on the IG-TTD in the deep water north of the SAF, but not beyond this limit.