Subglacial hydrology of the Lake Michigan Lobe, Laurentide Ice Sheet

• Main Author: Breemer, Christopher W.
• Other Authors: Clark, Peter U., Geosciences, Oregon State University. Graduate School
• Format: Master Thesis
• Language: English; unknown
• Published: Oregon State University
• Subjects: Hydrogeology; Ice sheets; Antarc*; Antarctic; Ice Sheet; Ice Stream B
• Online Access: https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/3f462866b

Fast ice flow and unstable ice sheet behavior were characteristic features of the Lake Michigan Lobe of the southern Laurentide Ice Sheet. Such behavior may result from some combination of subglacial-sediment deformation and decoupled sliding at the ice-bed interface. Both mechanisms depend on high water pressure relative to ice pressure. Using the finite-difference groundwater modeling package MODFLOW we simulate groundwater flow along a 1,040 km flowline, extending from the south shore of Lake Superior to the Mississippi River near Carbondale, Illinois. Model simulations indicate that subglacial aquifers were not capable of evacuating the estimated basal meltwater. A basal drainage system consisting of a distributed film or canal system, similar to systems hypothesized as underlying Ice Stream B, West Antarctic Ice Sheet, would transmit sufficient water to prevent basal water pressure from exceeding the ice overburden pressure. The buried Mahomet bedrock valley system may have drained enough subglacial meltwater to stop the advance of the Lake Michigan Lobe. Simulations also suggest that groundwater flow directions and velocities were substantially different than modern conditions.