Predicting the future hydrology of Arctic watersheds dominated by thermokarst lakes

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Across extensive areas of the Arctic, watersheds are dominated by immense numbers of lakes that cover up to 50% of the land area and are linked together in complex streamflow networks. Where the permafrost is ice rich, many of these lakes are thermokarst lakes that exist in closed depressions formed by settlement of the ground during earlier episodes of thawing of ice rich permafrost. These lakes and their linked streamflow networks are entering a new stage of rapid and dramatic transformation as the Arctic warms and precipitation changes. Although climate is a strong driver of the hydrology of these networks, changes are also driven by interactions and feedbacks between changing vegetation, snowcover, ice rich permafrost thaw, and related ground surface subsidence. These changes are ongoing with lakes growing, shrinking, forming; and completely being removed from the landscape. Understanding ongoing changes to these systems is extremely difficult and beyond our current modelling ability. This is true for both changes expected to occur over the next decade, but also over the coming centuries as changes to vegetation and permafrost continue will continue long after the global temperature is stabilized, as the vegetation, permafrost and hydrology slowly equilibrate with the new climate. We require a new generation of predictive methods to develop scenarios of such long-term change and allow us to address key issues related to the importance of these systems to northern society, indigenous land claims regions, wildlife habitat, and climate feedbacks. This knowledge is essential to guide decisions needed to meet Canada's national and international agreements to limit greenhouse gas emissions to a level that will ensure the long-term preservation of these unique Arctic ecosystems. Our existing ability to predict the hydrology of these systems is extremely poor, including: hydrologic and climate data across the Arctic is extremely sparse, often of low quality, and not spatially distributed; the extreme spatial heterogeneity of these Arctic watersheds is poorly documented and challenges our ability to measure and model these systems; existing hydrologic models poorly represent this variability as they don't integrate surface and subsurface hydrology, lakes, vegetation, and permafrost; and ground thermal/hydrologic models do not include ground subsidence and feedbacks related to snow accumulation. This DG will address key issues in my overarching, multiple-decade Arctic research program that is focussed on addressing these knowledge and modelling limitations, with the overall goal to undertake transformative hydrological research to document past changes to the hydrology of the Canadian Arctic, provide realistic scenarios of the changes in Arctic hydrology under future climate change scenarios.