Runoff generation in thawing discontinuous permafrost terrains

南泰加平原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速度和相关的人类干扰。该地区的永久冻土相对温暖、薄且不连续。其结果是，永久冻土层广泛融化，往往导致森林永久冻土层转变为无永久冻土、无树木的湿地。这种永久冻土融化引起的土地覆盖变化有可能破坏水文循环。然而，这种由永久冻土融化引起的土地覆盖转变的水文含义仍然知之甚少，尽管它已被证明在泛北极地区发生。因此，迫切需要提高对永久冻土融化及其水文后果的理解和预测能力。我的研究计划将开发和调动有关永久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。野外测量将集中在沿南至北约300公里横断面的三个观测站，横断面延伸到以泥炭地为主的不连续永久冻土层南部边缘。该样带非常适合研究多年冻土融化引起的生态系统变化及其对地表水文的影响，因为它涵盖了沿气候梯度的广泛的多年冻土生态系统特征。每个节点将实现以下具体目标：1)绘制过去60年来多年冻土、湿地和森林覆盖的空间变化分布图；2)针对不同的地面融湿条件，开展实地研究，提高对径流量和径流时间的认识；3)模拟控制径流的主要水通量和蓄水过程；4)通过野外调查和随后的区域尺度多年冻土模式的适应，提高在更大尺度上表征多年冻土影响的能力；5)在气候变暖和人为干扰的可能情景下，估算未来径流和地表水储存量。提高对永久冻土融化模式、速率、影响和反馈的认识和预测能力，将减少未来淡水供应的不确定性，从而改善水的规划、管理和安全，并使缓解战略能够更好地抵消负面影响。

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.