Can Deep Groundwater Influx be Detected from the Geochemistry of Thermokarst Lakes in Arctic Alaska?

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Copyright © 2016 John Wiley & Sons, Ltd. In the continuous permafrost zone, unfrozen ground may exist beneath large lakes and streams. Sub-lake taliks that extend through permafrost provide a potential conduit for subpermafrost groundwater to reach the surface, increasing dissolved ion concentrations in lake water. Twenty-eight lakes on the Arctic Coastal Plain of northern Alaska were sampled in 2013–14 to determine whether a difference in ionic concentration could be detected between lakes with and without through taliks. A thermal model originally developed by J. Ross Mackay indicated that 20 of the lakes may have a talik that penetrates the permafrost. Lake water samples were analysed for a variety of ions and geochemical properties. Generally, there was little interannual variation in ion concentration, pH and specific conductivity of lake water. Proximal lakes tended to have similar chemical signatures, but there were large variations across the study region. Local factors appeared largely to control lake water chemistry. Lakes with suspected through taliks did not demonstrate a hydrochemical signature distinct from nearby lakes lacking a through talik. This suggests that either: (1) there is no hydrological connection with subpermafrost groundwater due to aquicludes in the subsurface; (2) the flux of groundwater is too small to have a measurable impact on lake water chemistry; or (3) the steady-state condition for talik configuration assumed in the thermal model is not justified. Copyright © 2016 John Wiley & Sons, Ltd.

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Permafrost and Periglacial Processes