Seltzer Alan M, Ng Jessica, Danskin Wesley R, Kulongoski Justin T, Gannon Riley S, Stute Martin, Severinghaus Jeffrey P
Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA.
California Water Science Center, United States Geological Survey, 4165 Spruance Road, San Diego, CA, 92101, USA.
Nat Commun. 2019 Dec 16;10(1):5739. doi: 10.1038/s41467-019-13693-2.
Constraining the magnitude of past hydrological change may improve understanding and predictions of future shifts in water availability. Here we demonstrate that water-table depth, a sensitive indicator of hydroclimate, can be quantitatively reconstructed using Kr and Xe isotopes in groundwater. We present the first-ever measurements of these dissolved noble gas isotopes in groundwater at high precision (≤0.005‰ amu; 1σ), which reveal depth-proportional signals set by gravitational settling in soil air at the time of recharge. Analyses of California groundwater successfully reproduce modern groundwater levels and indicate a 17.9 ± 1.3 m (±1 SE) decline in water-table depth in Southern California during the last deglaciation. This hydroclimatic transition from the wetter glacial period to more arid Holocene accompanies a surface warming of 6.2 ± 0.6 °C (±1 SE). This new hydroclimate proxy builds upon an existing paleo-temperature application of noble gases and may identify regions prone to future hydrological change.
限制过去水文变化的幅度可能会增进对未来水资源可利用性变化的理解和预测。在此，我们证明地下水位深度（一种对水文气候敏感的指标）可以利用地下水中的氪和氙同位素进行定量重建。我们首次高精度（≤0.005‰ 原子质量单位；1σ）测量了地下水中这些溶解的惰性气体同位素，其揭示了补给时土壤空气中重力沉降所设定的与深度成正比的信号。对加利福尼亚地下水的分析成功再现了现代地下水位，并表明在末次冰消期南加利福尼亚的地下水位深度下降了17.9 ± 1.3米（±1标准误差）。这种从较湿润的冰期到更干旱的全新世的水文气候转变伴随着6.2 ± 0.6°C（±1标准误差）的地表变暖。这种新的水文气候代理基于现有的惰性气体古温度应用，可能识别出未来容易发生水文变化的区域。
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