Enhancing Understanding of the Hydrological Cycle via Pairing of Process‐Oriented and Isotope Ratio Tracers
Enhancing Understanding of the Hydrological Cycle via Pairing of Process‐Oriented and Isotope Ratio Tracers
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DOI：
10.1029/2021ms002648
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发表时间：
2021-09
影响因子：
6.8
通讯作者：
R. Fiorella;N. Siler;J. Nusbaumer;D. Noone
中科院分区：
文献类型：
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作者：
R. Fiorella;N. Siler;J. Nusbaumer;D. Noone
水文循环通过蒸发、水分输送和降水将地球的能量和碳预算耦合起来。尽管有大量的观测和模型，但我们推断水文循环最基本特性的能力仍然存在根本限制，包括水在大气中停留时间（RT）的空间模式以及从蒸发源到降水汇的平均距离。与此同时，稳定水同位素比等地球化学示踪剂提供了探测水文过程的工具，但尽管使用了几十年，但它们的解释仍然模棱两可。因此，需要新的机械工具将水同位素比的变化与潜在的水文过程联系起来。在这里，我们提出了一套新的“面向过程的标签”，我们用它来明确追踪同位素启用的社区大气模型版本 6 (iCAM6) 内的水文过程。使用这些标签，我们测试了降水同位素比率对地块降雨、大气 RT 变化的响应的假设，并保存有关蒸发期间气象条件的信息。我们提供了 1980 年至 2004 年历史模拟的结果，这些结果是根据 ERA5 再分析的风进行的。我们发现强有力的证据表明降水同位素比记录了蒸发过程中大气降水和气象条件的信息，但几乎没有证据表明降水同位素比随水汽RT变化。这些新的示踪剂方法将使现代水文循环中同位素比率的观测或过去陆地环境的代理与这些观测背后的环境过程之间建立更强有力的联系。
The hydrologic cycle couples the Earth's energy and carbon budgets through evaporation, moisture transport, and precipitation. Despite a wealth of observations and models, fundamental limitations remain in our capacity to deduce even the most basic properties of the hydrological cycle, including the spatial pattern of the residence time (RT) of water in the atmosphere and the mean distance traveled from evaporation sources to precipitation sinks. Meanwhile, geochemical tracers such as stable water isotope ratios provide a tool to probe hydrological processes, yet their interpretation remains equivocal despite several decades of use. As a result, there is a need for new mechanistic tools that link variations in water isotope ratios to underlying hydrological processes. Here we present a new suite of “process‐oriented tags,” which we use to explicitly trace hydrological processes within the isotopically enabled Community Atmosphere Model, version 6 (iCAM6). Using these tags, we test the hypotheses that precipitation isotope ratios respond to parcel rainout, variations in atmospheric RT, and preserve information regarding meteorological conditions during evaporation. We present results for a historical simulation from 1980 to 2004, forced with winds from the ERA5 reanalysis. We find strong evidence that precipitation isotope ratios record information about atmospheric rainout and meteorological conditions during evaporation, but little evidence that precipitation isotope ratios vary with water vapor RT. These new tracer methods will enable more robust linkages between observations of isotope ratios in the modern hydrologic cycle or proxies of past terrestrial environments and the environmental processes underlying these observations.