INFLUENCE OF BED HIGHS ON ICE FLOW AS DETERMINED BY BEDFORM MORPHOLOGY

Topographic highs across glaciated landscapes have the potential to temporarily slow or stabilize glacial ice flow or, conversely, increase ice flow through strain heating and subglacial meltwater production. Isolated bedrock highs across the deglaciated landscape of the Cordilleran Ice Sheet (CIS) in the Puget Lowland, Washington present the opportunity to assess the role of variable-size topographic highs in influencing ice-bed interactions and ice flow. By assessing a single glacial system using high-resolution digital elevation models, results will not be influenced by confounding variables that affect different systems such as local (glacial) climate. This work will utilize semi-automatic mapping techniques of subglacial bedforms to characterize bedform morphometrics including density, amplitude, elongation, and orientation to resolve changes in the subglacial environment of the extinct CIS. Subglacial streamlined bedforms will be identified upstream, on top of, and downstream of nine isolated topographic highs and statistically compared using a nonparametric Friedman test. Early results indicate topographic highs with the least amount of volume support bedform orientations most similar to regional ice flow directions, unlike the localized flow re-organization that develops around larger topographic highs with a “bump” volume of greater than 12 km³. An additional result identifying an increase in density, number, and elongation ratio range of bedforms downstream of the topographic highs suggest that strain heating and flow acceleration increases subglacial meltwater production, sediment transport, and variability in bedform production/maturity. While specific topographic threshold values vary by glacial system depending on local conditions, this process-based approach to assess the role of topographic highs on ice dynamics will elucidate general subglacial processes that can be widely applied to both deglaciated and contemporary glacial systems. Finalized results from this work will be extrapolated to subglacial topographic highs across contemporary glacial systems to determine the likelihood of increased subglacial meltwater production and ice velocity variations around these locations.