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

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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.