SUPRA-PERMAFROST TALIKS IN THAWING LANDSCAPES OF BOREAL ALASKA, USA (Invited Presentation)

Recently, there has been focused attention on the development of supra-permafrost taliks (perennially unfrozen zones in permafrost) that follows active-layer thickening in the sequence of top down permafrost-thaw progression in high latitudes. Talik formation can substantially influence geomorphic, hydrologic, and biogeochemical processes in permafrost landscapes, thus motivating efforts to understand current talik distribution and provide constraints on future evolution under changing climate. Here we present examples of talik formation in contrasting field sites in upland and lowland boreal forest ecoregions in interior Alaska, USA. Sites are located near the broadly mapped transition between continuous and discontinuous permafrost. Multiple lines of geophysical data provide support for enhanced talik development in response to disturbance, including wildfire and ice jam river flooding, superimposed on atmospheric warming. Drawing from results of cryohydrogeologic model simulations, field measurements, and additional analytical assessments, we discuss hydrologic implications for talik development and permafrost thaw acceleration at our contrasted sites. We identify and explore landscape characteristics and initial thermal conditions that control the propensity for talik development. Field investigations show localized examples of rapid talik development that outpace current coarse scale talik projections under the most extreme greenhouse gas emission scenario by ~ 100 years. Though large-scale extrapolation of localized extremes is not advised, our research raises questions regarding the potential for aggregated localized thaw to evolve toward regional importance as widespread wildfire activity and flooding intensify in the future.