A supply-limited model for cold-aeolian activity

Abstract

Aeolian activity which occurs under sub-zero temperatures over frozen sediment is termed cold-aeolian. These phenomena are found seasonally and perennially cold regions. Cold-aeolian processes effect significant amounts of sediment movement, produce distinctive cold-season landscapes and develop striking depositional features. Research on cold-aeolian phenomena has been largely qualitative and fragmented to this point. Quantitative field measurements of processes are extremely rare.

This dissertation uses controlled experiments and field measurements to generate a model for cold-aeolian activity. Wind erosion of frozen sediments is governed by pore-ice cohesion which limits the supply of sediments to aeolian processes. Controlled-temperature experiments explore the relationship between surface temperature and water content, delineating the cohesion boundaries for various aeolian processes. Small amounts of frozen pore-water can exert considerable restrictions on sediment movement. In the context of these limitations, pore-ice sublimation is the mechanism by which sediments are released from the surface and become available to entrainment by wind. Field experiments define the rate of particle release in terms of microclimate and surface conditions. The quantitative information on the supply limitations of pore-ice cohesion and supply mechanisms of pore-ice sublimation are incorporated into a general model of cold-aeolian activity. Other limits to movement in the cold environment, such as snow and ice cover, are also included in the assessment of aeolian activity. Winter field measurements from Presqu'ile Beach on the north shore of Lake Ontario provide data to test model accuracy. There is reasonable agreement between model predictions and field measurements, but the results point to the need for more research.

The dissertation is a significant body of work within the field of cold-aeolian research. Field measurements have produced quantitative information which is unprecedented in the study of cold-region aeolian activity. These measurements demonstrate that cold-aeolian processes account for a significant amount of sediment movement and geomorphic change, both readily visible in the Presqu'ile beach and dune complex. The model, presented as a computer simulation, is a practical tool for both managers and researchers. The model also serves as a conceptual framework for cold-aeolian activity and can play an important role in integrating this new field of research with mainstream aeolian geomorphology.