Land-water linkages and the biogeochemical effects of permafrost thaw: From pore waters to watersheds and beyond

气候变化正在从根本上改变我们这个星球的地球系统和社会制度。这一点在北方尤为明显，那里的永久冻土融化正在释放之前被锁在冻土中的物质，以便参与当代的生物地球化学循环。尽管我们理解这一过程大大增加了碳和其他生物地球化学组分从陆地向活跃性淡水环境的移动，但我们对这种变化将如何影响更广泛的生物地球化学循环的理解存在几个明显的差距。这些问题包括缺乏探索融化对风化的影响的研究；在淡水研究中对溶解物种而不是颗粒状物种的过度关注；对生物地球化学反应如何向下游传播的了解不足；以及缺乏记录特定地区的地形属性如何限制释放出的物质的浓度和反应性的研究。鉴于新的发现表明，北方的风化正在加速，颗粒(通过沉积物动员)往往主导着融化的物质从陆地到水的运输，显然，我们目前对永久冻土融化和当代生物地球化学循环之间的反馈的理解基本上是不完整的。我的NSERC资助的工作的地理焦点是加拿大西部北极的皮尔高原，由于它位于最后一次冰川最大时期的边界，那里拥有厚厚的晚更新世起源的冰盖，其中嵌入了大量的地面冰。这使得高原非常容易受到融化驱动的崩塌(热喀斯特)的影响，这与世界各地的冰川边缘景观相似。在过去的5年里，我的团队一直在这个地区工作，以证明无机和与颗粒相关的过程对于调节融化的生物地球化学反应的重要性。在接下来的5年里，我建议通过在分水岭、分水岭间和区域间尺度上的工作来扩大这一基础。具体地说，我将评估：(1)崩塌释放的物质如何通过崩塌显著影响的焦点流域传播；(2)永久冻土融化的生物地球化学特征如何在不同的扰动梯度之间变化；(3)陆地-水碳通量的大小和去向在不同的永久冻土组成区域之间如何不同。这种努力的扩大将发生在整个皮尔高原，以及加拿大西部北极其他地区的目标地点。除了关键地扩展我们对融化的生物地球化学效应的理解外，这项研究还将为HQP干部提供必要的后勤、实验室、分析和写作技能，使他们很快具备解决生物地球和地球系统科学中新出现的问题的资格。它还将使北方居民和社区组织贯穿始终。我期待着在加拿大西部北极地区进行这项研究。

Climate change is fundamentally altering our planet's Earth systems and social systems alike. Nowhere is this truer than in the north, where permafrost thaw is liberating materials previously locked up in frozen ground for participation in contemporary biogeochemical cycles. Although we understand that this process is substantially increasing the movement of carbon and other biogeochemical constituents from land to reactive freshwater environments, there exists several striking gaps in our understanding of how this change will affect broader biogeochemical cycles. These include a dearth of research exploring the effects of thaw on weathering; an overwhelming focus on dissolved, rather than particulate, species in freshwater studies; poor knowledge of how biogeochemical reactions propagate downstream; and a paucity of studies documenting how region-specific landscape attributes constrain the concentration and reactivity of liberated materials. Given emerging findings that weathering is accelerating in the north, and that particles (via sediment mobilization) often dominate thaw-enabled material transport from land to water, it seems clear that our current understanding of feedbacks between permafrost thaw and contemporary biogeochemical cycles is substantially incomplete. The geographic focus of my NSERC-funded efforts is the Peel Plateau in the western Canadian Arctic, which - because of its positioning at the boundary of the last glacial maximum - hosts thick deposits of late Pleistocene-origin tills that are embedded with substantial ground ice. This renders the Plateau highly susceptible to thaw-driven slumping (thermokarst), similar to glacial margin landscapes worldwide. Over the past 5 years, my group has worked in this region to document the importance of inorganic and particle-associated processes for regulating the biogeochemical response to thaw. Over the coming 5 years, I propose to expand on this foundation via work at watershed, inter-watershed, and inter-regional scales. Specifically, I will assess: (1) How the transport, and processing, of slump-released materials propagate through focal watersheds significantly affected by slumping; (2) how the biogeochemical signature of permafrost thaw varies across gradients of disturbance; and (3) how the magnitude, and fate, of land-water carbon flux differs between regions of variable permafrost composition. This expansion of effort will occur across the Peel Plateau, and in targeted sites elsewhere in the western Canadian Arctic. In addition to critically expanding our understanding of the biogeochemical effects of thaw, this research will provide a cadre of HQP with the logistical, laboratory, analytical, and writing skills necessary to become imminently qualified to tackle emerging issues in the biogeo- and Earth systems sciences. It will also involve northern residents and community organization throughout. I look forward to taking on this research in the western Canadian Arctic.