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的地球系统和社会系统。这一点在北方表现得最为明显，那里的永久冻土解冻正在释放以前被锁在冻土中的物质，让它们参与当代的生物地球化学循环。虽然我们知道这一过程大大增加了碳和其他生物地球化学成分从陆地到活性淡水环境的运动，但在我们对这种变化如何影响更广泛的生物地球化学循环的理解上存在几个显著的差距。其中包括缺乏探索解冻对风化影响的研究；在淡水研究中，过度关注溶解物种，而不是颗粒物种；缺乏生物地球化学反应如何向下游传播的知识；而记录区域特定景观属性如何限制释放物质的浓度和反应性的研究也很少。考虑到北方的风化正在加速，并且颗粒（通过沉积物动员）经常主导融化使物质从陆地到水中的运输，似乎很明显，我们目前对永久冻土融化和当代生物地球化学循环之间反馈的理解基本上是不完整的。

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.