Appalachian pasts, Arctic futures: permafrost landscape response to warming
Open Access
- Author:
- Del Vecchio, Joanmarie
- Graduate Program:
- Geosciences
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- May 07, 2021
- Committee Members:
- Sarah Ivory, Major Field Member
Erica Smithwick, Outside Unit & Field Member
Elizabeth Hajek, Major Field Member
Roman DiBiase, Chair & Dissertation Advisor
Mark Patzkowsky, Program Head/Chair - Keywords:
- geomorphology
permafrost
periglacial
cosmogenic
radiocarbon
morphometry
Arctic
Alaska
Appalachia
Last Glacial Maximum - Abstract:
- Understanding climate controls on topography and erosion rates reveal the underlying mechanisms operating on the landscape, allowing us to predict landscape response to climate perturbations. The onset of Quaternary glaciations represents a large climate perturbation to the Earth system, though a comparable climate shift is occurring today. Adjacent to continental ice sheets were cold but unglaciated landscapes underlain by permafrost, or perennially frozen soils. These periglacial landscapes would be particularly sensitive to warming: climate modulates soil erodibility, hydrology, and vegetation, such that erodibility varies not only in space but time on seasonal and millennial timescales. The unique combination of hillslope and fluvial processes of permafrost landscapes imply that there could be an erosional and topographic “signature” of permafrost processes compared to temperate climates. In this dissertation I explore whether and how the shape of the hillslopes and channels, as well as long-term erosion rates, are adjusted to periglacial conditions compared to temperate climates. I focus on the central Appalachian Mountains, which, like other mid-latitude settings, was underlain by permafrost during previous glacial periods, yet the relative magnitude of erosion during warm and cold climates, as well as in transition periods, remains unquantified. I generate a high-resolution climate and erosion record of a single warming phase to determine how specific climate factors affect hillslope erosion mechanisms. I pair these results with a Quaternary erosion record to show that periglacial conditions promote efficient hillslope erosion compared to temperate conditions. I then demonstrate that the permafrost-mediated hillslope and channel erosion dynamics inferred from sedimentary archives is also borne out in hillslope-channel form on paleoclimate gradients in central Appalachia. This thesis isolates the mechanisms through which periglaciation affects erosion rates and processes and quantifies the role past climates have played in Appalachia’s modern geomorphology. I also show that these principles can be used to identify erosion signatures of ongoing warming in Arctic landscapes.