Runoff generation in thawing discontinuous permafrost terrains

泰加平原南部生态区是地球上变暖最快的地区之一，正在经历前所未有的工业扩张和相关的人类干扰。该地区多年冻土相对温暖、薄且不连续。因此，冻土融化是普遍的，往往导致森林的冻土地形转化为无冻土，少树的湿地。这种冻土融化引起的土地覆盖变化有可能破坏水文循环。然而，尽管这种永久冻融引起的土地覆被变化表现出泛北极的发生，但其水文影响仍然知之甚少。因此，迫切需要更好地了解和预测永久冻土融化及其水文后果的能力。我的研究计划将开发和动员关于冻土融化引起的土地覆盖变化及其水文影响的新知识;并利用这些新知识开发一套新的预测水文建模工具。实地测量将集中在位于沿着一条约300 km的南北样带上的三个观测站，该样带延伸到泥炭地为主的不连续永久冻土南部边缘。该样带非常适合研究冻土融化引起的生态系统变化及其对地表水文的影响，因为它涵盖了沿着气候梯度的各种冻土生态系统特征。每个节点将实现以下具体目标：1）绘制过去60年来冻土、湿地和森林覆盖率变化的空间分布图; 2）针对不同的地面解冻和湿度条件，进行实地研究，以增进对径流量和时间的了解; 3）模拟控制径流的主要水通量和蓄水过程; 4）通过实地调查和随后对区域尺度永久冻土模型的调整，提高在更大尺度上描述永久冻土影响的能力; 5）在气候变暖和人类干扰的可能情景下，估计未来径流量和地表水储存量。提高对冻土融化模式、速率、影响和反馈的了解和预测能力，将通过减少未来淡水供应的不确定性来改善水资源规划、管理和安全，并使更好的缓解战略能够抵消负面影响。

The southern Taiga Plains ecoregion is one of the most rapidly warming regions on Earth, and is experiencing unprecedented rates of industrial expansion and related human disturbance. The permafrost in this region is relatively warm, thin and discontinuous. As a result, permafrost thaw is widespread and often leads to the transformation of forested permafrost terrains to permafrost-free, tree-less wetlands. Such permafrost thaw-induced landcover change has the potential to disrupt the hydrological cycle. However, the hydrological implications of this permafrost-thaw induced land cover transformation remain poorly understood despite its demonstrated pan-arctic occurrence. As a result, there is an urgent need for an improved understanding of, and ability to predict permafrost thaw and its hydrological consequences. My research programme will develop and mobilise new knowledge on permafrost thaw-induced land-cover change and the resulting hydrological impact; and use this new knowledge to develop a new suite of predictive hydrological modelling tools. Field measurements will concentrate on three observatories located along a ~300 km south-to-north transect extending over the peatland-dominated southern fringe of discontinuous permafrost. This transect is ideally suited for the study of permafrost thaw-induced changes to ecosystems and the resulting impacts on surface hydrology, since it covers a wide range of permafrost ecosystem characteristics along a climate gradient. The following specific objectives will be met at each node: 1) Map the changing spatial distribution of permafrost, wetland and forest coverage over the past 60 years; 2) For different ground thaw and moisture conditions, conduct field studies to improve the understanding of the volume and timing of runoff; 3) Simulate the major water flux and storage processes controlling runoff; 4) Improve the ability to characterize permafrost impacts at larger scales through field investigation and subsequent adaptation of a regional-scale permafrost model; and 5) Estimate future quantities of runoff and surface water storage under possible scenarios of climate warming and human disturbance. Improved knowledge and predictive capacity of permafrost thaw patterns, rates, impacts and feedbacks will improve water planning, management and security by reducing the uncertainty on the future availability of freshwater, and enable better mitigation strategies to offset negative impacts.