Potential mechanistic causes of increased baseflow across northern Eurasia catchments underlain by permafrost
Potential mechanistic causes of increased baseflow across northern Eurasia catchments underlain by permafrost
复制标题
DOI：
10.1002/hyp.13759
复制
发表时间：
2020-04
影响因子：
3.2
通讯作者：
S. Evans;Brandon A. Yokeley;C. Stephens;Benjamin Brewer
中科院分区：
文献类型：
--
作者：
S. Evans;Brandon A. Yokeley;C. Stephens;Benjamin Brewer
北极变暖的速度是全球平均速度的两倍，导致永久冻土融化和北极水文循环的重组，如低流量期间河流流量增加所示。在这些寒冷地区，多年冻土融化被假定为通过以下方式增加低流量排放或基流：（a）由于永久冻土层（称为活动层）上方冻融层增厚导致含水层渗透增加，地下水储存量和流向河流的流量局部增加，或（B）通过增强地下水，区域地下水循环长期增加-地表水的相互作用，由于几十年来广泛的永久冻土损失。虽然在整个北方欧亚大陆观测到基流增加，但精确的机械原因仍然难以捉摸。在这项研究中，我们区分这两个地下的物理机制基流增加发生的基流衰退分析使用每日径流记录从1913年至2003年在欧亚大陆北方的139个站根据不同的多年冻土面积范围。结果表明，从1913年到2003年，大多数集水区下覆连续多年冻土有增加的趋势，在其退流拦截，增加活动层厚度的代理。或者，大多数集水区下面的永久冻土类型在空间上不太广泛（例如，不连续的，零星的，孤立的，或没有永久冻土）有下降的趋势，在他们的衰退流拦截，表明在活动层厚度的潜在增加是不是在这些集水区基流变化的驱动因素。这可能表明，在集水区下方的连续多年冻土，活动层增厚与基流的增加，而在其他集水区与不太广泛的多年冻土，基流的增加可能是由批发多年冻土损失和垂直talik扩大，提高区域地下水循环。这项工作的结果可能会告知我们的地下机制负责改变北极水文循环的理解。
Warming in the Arctic is occurring at twice the rate of the global average, resulting in permafrost thaw and a restructuring of the Arctic hydrologic cycle as indicated by increased stream discharge during low‐flow periods. In these cold regions, permafrost thaw is postulated to increase low‐flow discharge, or baseflow, through either: (a) localized increases in groundwater storage and discharge to streams due to increased aquifer transmissivity from thickening of the freeze–thaw layer above permafrost known as the active layer or (b) long‐term increases in regional groundwater circulation via enhancement of groundwater–surface water interactions due to extensive permafrost loss over decades. While increasing baseflow has been observed throughout northern Eurasia, the precise mechanistic causes remain elusive. In this study, we differentiate between where these two subsurface physical mechanisms of baseflow increase are occurring by performing a baseflow recession analysis using daily streamflow records from 1913 to 2003 for 139 stations in northern Eurasia underlain by varying permafrost areal extents. Results indicate that from 1913 to 2003, the majority of catchments underlain by continuous permafrost have an increasing trend in their recession flow intercepts, a proxy for increasing active layer thickness. Alternatively, the majority of catchments underlain by permafrost types that are less spatially extensive (e.g., discontinuous, sporadic, isolated, or no permafrost) have decreasing trends in their recession flow intercepts, indicating that a potential increase in active layer thickness is not the driving factor of baseflow variations in these catchments. This may indicate that in catchments underlain by continuous permafrost, active layer thickening correlates with increases in baseflow, whereas, in other catchments with less extensive permafrost, increases in baseflow may be caused by wholesale permafrost loss and vertical talik expansion that enhances regional groundwater circulation. The results of this work may inform our understanding of the subsurface mechanisms responsible for the changing Arctic hydrologic cycle.