SURFACE WATER – GROUNDWATER INTERACTIONS CONTRIBUTING TO ANNUAL AND SEASONAL SHRINKAGE OF ARCTIC LAKES

Lakes in Arctic delta environments act to smooth fresh river discharge rates to the Arctic Ocean, both filtering and serving as reservoirs for nutrients, sediments, and flood waters. Recent remote sensing studies show Arctic lakes in discontinuous permafrost zones are shrinking over seasonal and annual time scales with potential impacts on those mitigation roles. The shrinkage of these lakes are attributed to the heat transfer from relatively warm surface bodies to the surrounding permafrost. Surface water connectivity between channels and lakes serve as a pathway to introduce greater temperatures into isolated areas. The development of taliks (local permafrost thaw permafrost beneath surface water bodies) increases lake-groundwater connectivity, which promotes additional permafrost thaw and decreases Artic lake volume and surface area. We built numerical groundwater, heat flow, and transport models that incorporate freeze-thaw dynamics in FEFLOW to investigate the correlation between lake-channel proximity, and subsequent heat transfer and talik development to greater groundwater connectivity. These models are calibrated against in-situ temperature measurements from a Northern Alaska field season in summer 2021 to provide realistic boundary conditions. Preliminary results suggest lakes closest to the channel experience greater heat transfer and subsequent talik development while lakes furthest from the channel remain isolated. Understanding the changing dynamics of thermokarst lakes within Arctic deltas is critical for future mitigation efforts.