Cryostratigraphy and the Sublimation Unconformity in Permafrost from an Ultraxerous Environment, University Valley, McMurdo Dry Valleys of Antarctica

The cryostratigraphy of permafrost in ultraxerous environments is poorly known. In this study, icy permafrost cores from University Valley (McMurdo Dry Valleys, Antarctica) were analyzed for sediment properties, ground-ice content, types and distribution of cryostructures, and presence of unconformities. No active layer exists in the valley, but the ice table, a sublimation unconformity, ranges from 0 to 60 cm depth. The sediments are characterized as a medium sand, which classifies them as low to non-frost susceptible. Computed tomography (CT) scan images of the icy permafrost cores revealed composite cryostructures that included the structureless, porous visible, suspended and crustal types. These cryostructures were observed irrespective of ground-ice origin (vapour deposited and freezing of snow meltwater), suggesting that the type and distribution of cryostructures could not be used as a proxy to infer the mode of emplacement of ground ice. Volumetric ice content derived from the CT scan images underestimated measured volumetric ice content, but approached measured excess ice content. A palaeo-sublimation unconformity could not be detected from a change in cryostructures, but could be inferred from an increase in ice content at the maximum predicted ice table depth. This study highlights some of the unique ground-ice processes and cryostructures in ultraxerous environments

Towards the incorporation of hydrogeochemistry into the modelling of permafrost environments: a review of recent recommendations, considerations, and literature

This study is a meta-analysis of recent global research articles on hydrogeochemical modelling of permafrost regions to determine trends and consensus on research gaps and future research directions. The hydrogeochemical response of permafrost to climate change remains challenging to estimate and forecast despite evidence of large-scale impacts on freshwater and ecological cycles. We investigate the feasibility, need, and potential for hydrogeochemical modelling of permafrost landscapes by reviewing recommendations from previous modelling, review, and primer papers, including discussing ways to advance this type of modelling science. Key permafrost hydrogeochemical processes are discussed, including heat transfer and associated freeze–thaw regimes, biogeochemical processes and rates, and surface and subsurface flow. Modelling considerations (i.e., model dimension, scale, heterogeneity, and permafrost zonation) and model parameters are subsequently examined. Finally, limitations and additional considerations for advancing permafrost hydrogeochemical modelling efforts are reviewed. The findings of this review are summarized in recommendations, tables, and two schematics incorporating key considerations for future hydrogeochemical modelling initiatives in permafrost environments