Sensitivity of headwater streamflow to thawing permafrost and vegetation change in a warming Arctic
Sensitivity of headwater streamflow to thawing permafrost and vegetation change in a warming Arctic
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DOI：
10.1088/1748-9326/ac5f2d
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发表时间：
2022-04-01
影响因子：
6.7
通讯作者：
Terskaia, A.
中科院分区：
文献类型：
--
作者：
Koch, J. C.;Sjoberg, Y.;Terskaia, A.
气候变化有可能通过融化永久冻土，进而改变水文状况和植被分布、地貌和生产力，从而影响北极的源头河流。多年冻土融化和地下流量的增加是从大河的化学作用中推断出来的，但关于这对源头河流的影响的经验证据有限。在这里，我们展示了变化的植被覆盖和土壤融化如何通过水平衡、河流流量趋势和跨越阿拉斯加西北部地温梯度的化学变化来改变源头流域的水文。较冷的冻土带占主导地位的集水区通过溪流排放降水，而在森林面积较大的较温暖的集水区，蒸散(ET)和渗透是相当大的通量。森林土壤解冻较早，解冻时间较长，水分含量呈季节性下降，与较大的ET和入渗量一致。河床入渗和水化学表明，即使是轻微的变暖也会导致入渗量和地下径流的增加。北极的进一步变暖、永久冻土流失和植被变化将把水送回大气和许多地区的地下含水层，如果不通过增加降雨量来弥补的话，可能会大幅减少源头溪流的排放量。源头河流排放量的减少将对水生和河岸生态系统产生重要影响。
Climate change has the potential to impact headwater streams in the Arctic by thawing permafrost and subsequently altering hydrologic regimes and vegetation distribution, physiognomy and productivity. Permafrost thaw and increased subsurface flow have been inferred from the chemistry of large rivers, but there is limited empirical evidence of the impacts to headwater streams. Here we demonstrate how changing vegetation cover and soil thaw may alter headwater catchment hydrology using water budgets, stream discharge trends, and chemistry across a gradient of ground temperature in northwestern Alaska. Colder, tundra-dominated catchments shed precipitation through stream discharge, whereas in warmer catchments with greater forest extent, evapotranspiration (ET) and infiltration are substantial fluxes. Forest soils thaw earlier, remain thawed longer, and display seasonal water content declines, consistent with greater ET and infiltration. Streambed infiltration and water chemistry indicate that even minor warming can lead to increased infiltration and subsurface flow. Additional warming, permafrost loss, and vegetation shifts in the Arctic will deliver water back to the atmosphere and to subsurface aquifers in many regions, with the potential to substantially reduce discharge in headwater streams, if not compensated by increasing precipitation. Decreasing discharge in headwater streams will have important implications for aquatic and riparian ecosystems.