Effects of Future Increases in Tidal Flooding on Salinity and Groundwater Dynamics in Coastal Aquifers
Effects of Future Increases in Tidal Flooding on Salinity and Groundwater Dynamics in Coastal Aquifers
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DOI：
10.1029/2022wr033195
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发表时间：
2022-12-01
影响因子：
5.4
通讯作者：
Shen, Chengji
中科院分区：
文献类型：
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作者：
Heiss, James W.;Mase, Bryce;Shen, Chengji
未来由于海平面上升而引起的潮汐洪水频率的增加可能会影响沿海含水层中的孔隙水盐度。在这项研究中，我们利用数值变密度变饱和地下水流动和盐分运移模型研究了潮汐泛滥频率增加对沿海含水层盐度和流动动力学的影响。短(次日)和长(十年)周期潮汐与SLR预测相结合，以驱动连续80年的水流和盐分输送模型。结果表明，潮间带的侵蚀导致了上层含水层的周期性和长期的垂直盐碱化。由于潮汐泛滥，上层含水层盐碱化，迫使下界面向海，甚至在单反之下也是如此。系统动力学受SLR和与近地大潮有关的长周期潮汐强迫和18.6年月节周期的相互作用所控制。周期性的潮汐洪水极大地加强了潮间带咸水-淡水混合，导致在单反方案中，潮间带咸水-淡水混合区域扩大了6至10倍。扩张的开始恰逢潮汐分量幅度的月球节点循环导致的极高水位。这些发现首次证明了渐进式SLR和短周期潮汐和长周期潮汐对含水层盐度分布的综合影响，并揭示了SLR对咸水入侵的相互影响。随着世界范围内潮汐洪水的加剧，这一结果可能对沿海海洋化学通量和地下水资源产生重要影响。
Future increases in the frequency of tidal flooding due to sea level rise (SLR) are likely to affect pore water salinities in coastal aquifers. In this study, we investigate the impact of increased tidal flooding frequency on salinity and flow dynamics in coastal aquifers using numerical variable-density variably-saturated groundwater flow and salt transport models. Short (sub-daily) and long (decadal) period tides are combined with SLR projections to drive continuous 80-year models of flow and salt transport. Results show that encroaching intertidal zones lead to both periodic and long-term vertical salinization of the upper aquifer. Salinization of the upper aquifer due to tidal flooding forces the lower interface seaward, even under SLR. System dynamics are controlled by the interplay between SLR and long period tidal forcing associated with perigean spring tides and the 18.6-year lunar nodal cycle. Periodic tidal flooding substantially enhances intertidal saltwater-freshwater mixing, resulting in a 6- to 10-fold expansion of the intertidal saltwater-freshwater mixing area across SLR scenarios. The onset of the expansion coincides with extreme high water levels resulting from lunar nodal cycling of tidal constituent amplitudes. The findings are the first to demonstrate the combined effects of gradual SLR and short and long period tides on aquifer salinity distributions, and reveal competing influences of SLR on saltwater intrusion. The results are likely to have important implications for coastal ocean chemical fluxes and groundwater resources as tidal flooding intensifies worldwide.