EP061-0026
Relationship between nearshore bathymetry, winter shore ice and coastal erosion: A case study from the Laurentian Great Lakes, USA
Wednesday, 16 December 2020
Poster
Brittany Hartley, Michigan State University, East Lansing, MI, United States, Ethan J Theuerkauf, Michigan State University, Department of Geography, Environment, and Spatial Sciences, East Lansing, MI, United States, Lucas Zoet, University of Wisconsin-Madison, Geoscience, Madison, WI, United States, J Elmo Rawling III, University of Wisconsin Madison, Wisconsin Geological and Natural History Survey, Madison, WI, United States and Stefanie Dodge, University of Wisconsin Madison, Madison, WI, United States
Abstract:
Winter shore ice is common along cold climate coastlines; however, little is known about the role it plays in facilitating coastal erosion and sediment transport. A lack of observations and fundamental characterization of the spatial and temporal role that variable ice plays in driving erosion and sediment transport hinders coastal evolution models from accurately incorporating these processes. Shore ice is predominantly thought to buffer the coast from erosion; however, reduced winter ice cover and more frequent freeze-thaw cycles could change this dynamic. New remote sensing technologies create opportunities to document geomorphic changes associated with ice. This project aims to document geomorphic changes at both high and low energy sandy beaches in the Great Lakes region in response to varying degrees of winter shore ice, ranging from ephemeral, thin beach ice to expansive nearshore ice complexes that persist through the winter. These data aim to place winter shore ice into context with other coastal processes (e.g. storms) that drive patterns of erosion and sediment transport.
Preliminary field data confirm that a lack of shore ice cover can enhance coastal erosion from winter storms. A winter storm that struck a Lake Michigan study site in January 2020 when no shore ice was present, resulted in high magnitude erosion and overwash. Half of the erosion documented at this site over a 2-year period occurred within 2 days of the storm. The minimal ice cover at this site also allowed for an examination of the role shoreface bathymetry plays in controlling initial ice formation in a high-energy setting. Shore ice only began to form where the shoreface slope was shallow and did not form in locations with steep slopes, likely owing to the degree of wave breaking across these different shoreface morphologies. At another site on Lake Superior where wave energy was low and lake ice was persistent throughout the season bathymetry again was found to influence the nearshore ice complex morphology (i.e. location of ice ridges corresponded with bathymetric highs). These initial results suggest that bathymetry is a key parameter for accurately modeling the impacts of ice on erosion and sediment transport.
