Impacts of glacially recharged groundwater flow systems on talik evolution

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Abstract

Most currently permafrost-covered landscapes underwent fundamental shifts in the hydrogeological and the thermal regime as a result of deglaciation after the Last Glacial Maximum (LGM). The transient effects of heat and fluid flow associated with retreating ice sheets are important to consider for the present-day hydrogeology of these regions. In this paper, we use numerical models to evaluate the evolution of taliks underneath proglacial lakes during deglaciation. In our models, the hydrological and thermal boundary conditions at the lake site are constraint by the hydrogeological impacts of ice sheet dynamics since the LGM. During the LGM, the ground surface was insulated from air temperatures, and as a result, there was no permafrost underneath the wet-based ice. Subsequently, ice sheet retreat led to an exposure of a proglacial area to subzero air temperatures and the formation of permafrost. Where proglacial lakes form, discharge of deeper groundwater becomes focused. In this scenario, subpermafrost groundwater flow is driven by a combination of direct subglacial recharge and elevated hydraulic heads preserved in that part of the aquifer. Advective heat flow can delay or prevent through taliks from freezing as function of aquifer properties. The presence and evolution of through taliks in thick permafrost can create complex and transient hydrogeological phenomena.

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