Stable isotopes as an indicator of open taliks in a discontinuous and degrading permafrost aquifer

The unpredictable distribution and configuration of permafrost in discontinuous permafrost aquifers located in sub arctic river flood plains presents uncertainties in the delineation of groundwater flow in these aquifers. At the extreme, the upward flow of subpermafrost groundwater through open taliks into suprapermafrost groundwater can redirect the flow of groundwater in the suprapermafost portion of an aquifer by as much as ninety degrees. Identification of open taliks in discontinuous permafrost is challenging short of extensive monitoring well networks consisting of shallow and deep clustered wells or advanced geophysical methods. Hydrological studies over the last number of decades have shown the usefulness of stable isotopes for characterizing groundwater flow in various types of aquifers; deuterium (H-2) and oxygen-18 (O-18) being the most widely used for this purpose. Here we present H-2 and O-18 results from an extensively monitored flood plain aquifer located in discontinuous permafrost. Results show a distinct difference in groundwater isotopic values between areas where open taliks exist and areas underlaid by permafrost. Differences between isotopic values are attributed to differing levels of mixing of precipitation recharge with glacial fed river water recharging the aquifer. Using the distinct differences between isotopic values we propose a conceptual flow model for flood plain aquifers in discontinuous permafrost environments.