Numerous studies utilizing remote sensing imagery and other methods have documented that thermokarst lakes are undergoing varied hydrological transitions in response to recent climate changes, from surface area expansion to drainage and evaporative desiccation. Here, we provide a synthesis of hydrological conditions for 376 lakes of mainly thermokarst origin across high-latitude North America. We assemble surface water isotope compositions measured during the past decade at five lake-rich landscapes including Arctic Coastal Plain (Alaska), Yukon Flats (Alaska), Old Crow Flats (Yukon), northwestern Hudson Bay Lowlands (Manitoba), and Nunavik (Quebec). These landscapes represent the broad range of thermokarst environments by spanning gradients in meteorological, permafrost, and vegetation conditions. An isotope framework was established based on flux-weighted long-term averages of meteorological conditions for each lake to quantify water balance metrics. The isotope composition of source water and evaporation-to-inflow ratio for each lake were determined, and the results demonstrated a substantial array of regional and subregional diversity of lake hydrological conditions. Controls on lake water balance and how these vary among the five landscapes and with differing environmental drivers are assessed. Findings reveal that lakes in the Hudson Bay Lowlands are most vulnerable to evaporative desiccation, whereas those in Nunavik are most resilient. However, we also identify the complexity in predicting hydrological responses of these thermokarst landscapes to future climate change.
Please cite this article as: Narancic, B., Wolfe, B.B., Pienitz, R., Meyer, H., Lamhonwah, D., Landscape-gradient assessment of thermokarst lake hydrology using water isotope tracers, Journal of Hydrology (2016), doi: http:// dx.doi.org/10. 1016/j.jhydrol.2016.11.028 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.1 Landscape-gradient assessment of thermokarst lake hydrology using water isotope -Water isotopes are used to characterize thermokarst lake hydrology in Nunavik, Canada.-Rainfall and/or permafrost meltwater are the main lake water sources.-Maritime climate enhances the hydrological resiliency of thermokarst lakes.-Terrestrial carbon inputs from surface runoff are likely to increase in the future.-Thermokarst lakes will persist and methane emissions are likely to increase.3 ABSTRACT Thermokarst lakes are widespread in arctic and subarctic regions. In subarctic Québec (Nunavik), they have grown in number and size since the mid-20 th century.Recent studies have identified that these lakes are important sources of greenhouse gases. This is mainly due to the supply of catchment-derived dissolved organic carbon that generates anoxic conditions leading to methane production. To assess the potential role of climate-driven changes in hydrological processes to influence greenhouse-gas emissions, we utilized water isotope tracers to characterize the water balance of thermokarst lakes in Nunavik during three consecutive mid-to late summer seasons (2012)(2013)(2014). Lake distribution stretches from shrub-tundra overlying discontinuous permafrost in the north to spruce-lichen woodland with sporadic permafrost in the south.Calculation of lake-specific input water isotope compositions ( I ) and lake-specific evaporation-to-inflow (E/I) ratios based on an isotope-mass balance model reveal a narrow hydrological gradient regardless of diversity in regional landscape characteristics. Nearly all lakes sampled were predominantly fed by rainfall and/or permafrost meltwater, which suppressed the effects of evaporative loss. Only a few lakes in one of the southern sampling locations, which overly highly degraded sporadic permafrost terrain, appear to be susceptible to evaporative lake-level drawdown. We attribute this lake hydrological resiliency to the strong maritime climate in coastal regions of Nunavik. Predicted climate-driven increases in precipitation and permafrost degradation will likely contribute to persistence and expansion of thermokarst lakes throughout the region. If coupled with an increase in terrestrial carbon inputs to thermokarst lakes from surface runoff, conditions favorable for mineralizatio...
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