Active Layer Groundwater Flow: The Interrelated Effects of Stratigraphy, Thaw, and Topography
Active Layer Groundwater Flow: The Interrelated Effects of Stratigraphy, Thaw, and Topography
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DOI：
10.1029/2018wr024636
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发表时间：
2019-08
影响因子：
5.4
通讯作者：
Michael T. O'Connor;M. Cardenas;B. Neilson;K. Nicholaides;G. Kling
中科院分区：
文献类型：
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作者：
Michael T. O'Connor;M. Cardenas;B. Neilson;K. Nicholaides;G. Kling
冻土上解冻“活土层”地下水流动的外部驱动因素和内部控制因素很少受到约束，因为它们是动态的和空间可变的。了解这些控制是至关重要的，因为地下水可以向地表水体提供溶质，如溶解的有机物。我们通过测量含水层几何形状、饱和厚度以及在北极一级流域内收集的两种主要景观类型的水力特性，计算了通过活动层的稳态三维超冻土地下水流量。饱和带的深度、位置和厚度是控制不同地点和不同时期地下水流量变化的主要因素。地下水位深度对地下水流的影响大于融化深度的影响。在低地表坡度（2-4%）的景观中，较高的地下水位和较厚的渗透性泥炭沉积物的结合导致了融季早期和晚期之间相对稳定的地下水流动。地表坡度较大（4-10%）的景观既有较深的地下水位，也有较薄的泥炭沉积物；这里通常观测到的渗透率随深度的下降比平坦地区更为明显，随着地下水位的下降，地下水流量在夏初和夏末之间显著减少。地下水流动也受到微地形特征的影响，这些特征保留了地下水，否则地下水会随着活动层的加深而释放出来。地下水和溶解有机质的主要来源可能是潮湿、平坦、有机层厚的地区。这一发现为现在和未来北极的流体流动和溶质输运动力学提供了信息。
The external drivers and internal controls of groundwater flow in the thawed “active layer” above permafrost are poorly constrained because they are dynamic and spatially variable. Understanding these controls is critical because groundwater can supply solutes such as dissolved organic matter to surface water bodies. We calculated steady‐state three‐dimensional suprapermafrost groundwater flow through the active layer using measurements of aquifer geometry, saturated thickness, and hydraulic properties collected from two major landscape types over time within a first‐order Arctic watershed. The depth position and thickness of the saturated zone is the dominant control of groundwater flow variability between sites and during different times of year. The effect of water table depth on groundwater flow dwarfs the effect of thaw depth. In landscapes with low land‐surface slopes (2–4%), a combination of higher water tables and thicker, permeable peat deposits cause relatively constant groundwater flows between the early and late thawed seasons. Landscapes with larger land‐surface slopes (4–10%) have both deeper water tables and thinner peat deposits; here the commonly observed permeability decrease with depth is more pronounced than in flatter areas, and groundwater flows decrease significantly between early and late summer as the water table drops. Groundwater flows are also affected by microtopographic features that retain groundwater that could otherwise be released as the active layer deepens. The dominant sources of groundwater, and thus dissolved organic matter, are likely wet, flatter regions with thick organic layers. This finding informs fluid flow and solute transport dynamics for the present and future Arctic.