Influence of permafrost distribution on groundwater flow in the context of climate‐driven permafrost thaw: Example from Yukon Flats Basin, Alaska, United States
Influence of permafrost distribution on groundwater flow in the context of climate‐driven permafrost thaw: Example from Yukon Flats Basin, Alaska, United States
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DOI：
10.1029/2011wr011595
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发表时间：
2012-07
影响因子：
5.4
通讯作者：
M. Walvoord;C. Voss;T. P. Wellman
中科院分区：
文献类型：
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作者：
M. Walvoord;C. Voss;T. P. Wellman
了解多年冻土在控制地下水流动路径和通量方面的作用，是评估气候变化对植被、物种栖息地、生物地球化学循环和生物多样性潜在影响的研究的核心。最近在阿拉斯加内陆的实地研究显示了水文变化的证据，这些变化假设是由永久冻土退化造成的。本研究评估了多年冻土的水文控制作用，阐明了不同空间多年冻土模式下的区域地下水流动模式，并评估了多年冻土退化的潜在水文后果。育空平原盆地（YFB）是育空河流域内的一个大的（118,340平方公里）子盆地，为这次调查提供了基础。模型模拟表明，随着多年冻土覆盖的减少，以下趋势：(1)向河流的地下水流量增加，与育空河流域基流观测的历史趋势一致；(2)总体地下水通量增加的潜力；(3)低地地下水流量的空间范围增加；(4)上层（浅层）地下水对总基流的贡献比例降低。这些趋势直接影响河流出口的化学成分和停留时间、受地下水影响的湖泊和湿地的状况、季节性河冰厚度和河流温度。目前，YFB被粗略地映射为跨越连续-不连续永久冻土过渡，模型分析表明这是一个临界阈值；因此，如果目前的永久冻土范围减少，YFB可能处于重大水文变化的边缘。这种可能性强调了通过地球物理技术、遥感和地面观测改进该地区永久冻土和其他水文地质信息特征的必要性。
Understanding the role of permafrost in controlling groundwater flow paths and fluxes is central in studies aimed at assessing potential climate change impacts on vegetation, species habitat, biogeochemical cycling, and biodiversity. Recent field studies in interior Alaska show evidence of hydrologic changes hypothesized to result from permafrost degradation. This study assesses the hydrologic control exerted by permafrost, elucidates modes of regional groundwater flow for various spatial permafrost patterns, and evaluates potential hydrologic consequences of permafrost degradation. The Yukon Flats Basin (YFB), a large (118,340 km2) subbasin within the Yukon River Basin, provides the basis for this investigation. Model simulations that represent an assumed permafrost thaw sequence reveal the following trends with decreasing permafrost coverage: (1) increased groundwater discharge to rivers, consistent with historical trends in base flow observations in the Yukon River Basin, (2) potential for increased overall groundwater flux, (3) increased spatial extent of groundwater discharge in lowlands, and (4) decreased proportion of suprapermafrost (shallow) groundwater contribution to total base flow. These trends directly affect the chemical composition and residence time of riverine exports, the state of groundwater‐influenced lakes and wetlands, seasonal river‐ice thickness, and stream temperatures. Presently, the YFB is coarsely mapped as spanning the continuous‐discontinuous permafrost transition that model analysis shows to be a critical threshold; thus, the YFB may be on the verge of major hydrologic change should the current permafrost extent decrease. This possibility underscores the need for improved characterization of permafrost and other hydrogeologic information in the region via geophysical techniques, remote sensing, and ground‐based observations.