The Arctic has experienced substantial warming during the past century with models projecting continued warming accompanied by increases in summer precipitation for most regions. A key impact of increasing air surface temperatures is the deepening of the active layer, which is expected to alter hydrological processes and pathways. The aim of this study was to determine how one of the warmest and wettest summers in the past decade at a High Arctic watershed impacted water infiltration and storage in deeply thawed soil and solute concentrations in stream runoff during the thaw period. In June and July 2012 at the Cape Bounty Watershed Observatory, we combined active layer measurements with major ion concentrations and stable isotopes in surface waters to characterize the movement of different runoff sources: snowmelt, rainfall, and soil water. Results indicate that deep ground thaw enhanced the storage of infiltrated water following rainfall. Soil water from infiltrated rainfall flowed through the thawed transient layer and upper permafrost, which likely solubilized ions previously stored at depth. Subsequent rainfall events acted as a hydrological flushing mechanism, mobilizing solutes from the subsurface to the surface. This solute flushing substantially increased ion concentrations in stream runoff throughout mid to late July. Results further suggest the importance of rainfall and soil water as sources of runoff in a High Arctic catchment during mid to late summer as infiltrated snowmelt is drained from soil following baseflow. Although there was some evaporation of surface water, our study indicates that flushing from solute stores in the transient layer was the primary driver of increased ion concentrations in stream runoff and not evaporative concentration of surface water. With warmer and wetter summers projected for the Arctic, ion concentrations in runoff (especially in the late thaw season), will likely increase due to the deep storage and subsurface flow of infiltrated water and subsequent flushing of previously frozen solutes to the surface.

Permafrost disturbances (such as active layer detachment (ALD) slides) and thermal perturbation (deep ground thaw from high soil temperatures) alter Arctic surface water chemistry. However, the potential multi-year impacts on water chemistry and the ultimate recovery time are not well understood. This study evaluates the impacts on surface waters and recovery following disturbance of a High Arctic catchment in 2007 from ALDs. We measured ion concentrations and stable isotopes in surface waters collected between 2006 and 2014 from paired catchments -one disturbed and the other not. The years 2007 and 2012 were exceptionally warm and represent unusual thermal perturbation for both catchments. Results indicate that the exposure and mobilization of soluble ions in near surface soil is a key control over dissolved ion concentrations and composition following ALDs. Runoff in the disturbed catchment shows increased total dissolved solute (TDS) concentrations and seasonal TDS fluxes and changes to the relative composition of individual ions in surface water. These impacts persisted for the 7 year study duration after disturbance and are consistent with the thawing of the solute-rich transient layer and upper permafrost. Thermal perturbation increased TDS concentrations and seasonal fluxes in runoff for up to 2 years, as ions released from ground thaw appear to be available for flushing in subsequent summers.Key words: permafrost disturbance, permafrost thaw, solutes, streamflow, active layer detachment.Résumé : Les perturbations du pergélisol (telles que les glissements causés par le détache-ment de la couche active (DCA)) et la perturbation thermique (le dégel du sol en profondeur causé par des températures élevées) changent l'hydrochimie des eaux de surface dans l'Arctique. Cependant, on ne comprend pas bien les impacts potentiels de plusieurs années sur l'hydrochimie ni le temps de rétablissement final. Cette étude évalue les impacts sur les eaux de surface après la perturbation For personal use only.changements de la composition relative des ions individuels dans les eaux de surface. Ces impacts ont continué pendant les sept ans de la durée de l'étude après la perturbation et sont conformes avec le dégel de la couche transitoire riche en solutés et du pergélisol supérieur. La perturbation thermique a causé l'augmentation des concentrations de SDT et des flux saisonniers du ruissellement sur une période allant jusqu'à deux ans alors que les ions émanant du dégel du sol semblent être disponibles pour lessivage au cours des étés suivants.Mots-clés : perturbations du pergélisol, dégel du pergélisol, solutés, écoulement fluvial, détachement de la couche active.

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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Canada is the world's largest producer of maple syrup. Syrup production depends on weather and climatic conditions of the sugarbush. However, forest ecosystems are highly sensitive to climate change. The effect of rapidly changing precipitation and temperature patterns on tree species is of concern as these long‐lived organisms cannot quickly adapt to the new environmental conditions in which they find themselves. As temperatures increase it is expected that there will be a change in species' ranges poleward. This study uses Multi‐Criteria Decision Making (MCDM) and Geographic Information System (GIS) weighted sum analysis to project near future (2050) and distant future (2100) suitability maps of sugar maple (Acer saccharum) habitat in Ontario associated with three different Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) scenarios. Our maps project an overall decrease in the amount of suitable habitat within the current sugar maple range under the scenarios modelled, which intensifies in the later time period. Furthermore there is a projected shift in central and southern Ontario from a region dominated by suitable habitat to one dominated by unsuitable habitat.