2018 CSDMS meeting-070
Using relict Pleistocene geomorphology to inform future permafrost change
A goal of the geomorphology community is to translate our understanding of past and present processes to predict landscape change in the future. Here we present our knowledge about relict permafrost landscapes across central Appalachia, and we propose a framework through which the geologic record and landscape models may be used to predict change in modern permafrost settings. The onset of Quaternary glacial cycles profoundly influenced the pace and pattern of erosion in mid-latitude settings through the development and subsequent degradation of perennially-frozen soils. Lidar-based mapping documents extensive periglacial alteration of the central Appalachian landscape, including solifluction lobes and other mass-wasting features. These features appear aspect-modulated, implying microclimate control. Geomorphic mapping, shallow geophysical imaging and cosmogenic nuclide dating reveal that periglacial erosion sets regolith patterns, subsurface architecture and erosion rates for multiple glacial cycles. Moreover, a combination of slow erosion rates and structural traps means headwater valleys and basins preserve direct records of upland erosional response to climate change, and planned work to core modern peat bogs may provide paleoclimate and paleoecological markers like pollen and leaf waxes in addition to quartz-rich debris for cosmogenic dating. Geologic data can be supplemented by permafrost hydrology models for an improved understanding of both the microclimate and long-term climate controls on periglacial hillslope processes. Informative models pair realistic active layer flow paths, accounting for both infiltration and permafrost thaw, with effective stress calculations to develop more accurate failure depth estimates. Such process-based models will be key to predicting future periglacial landscape change as warming exceeds historical trends.