1 Standing Senate Committee on Transport and Communications Impacts of climate change on transportation infrastructure in the Great Lakes and the St. Lawrence Seaway. February 27, 2024 Follow-up to questions at the hearing. Robin Davidson-Arnott, Professor Emeritus, University of Guelph Below are two diagrams that may provide additional clarity to questions related to historical lake level cycles and to the effect of isostatic changes at the outlet to Lakes Huron/Michigan at Sarnia. The graphs on page show the monthly mean water level in each of the lakes from to the present.

They show no significant change in the range of lake level over this period on any of the lakes.(Source: US Army Corps of Engineers) The map on page shows the effect of ongoing uplift of the outlet to Lake Huron on the shoreline of Lakes Huron and Michigan. 2 Change in shoreline elevation relative to the outlet to Lake Huron at Sarnia in cm/100 years. Areas with Green shading are emerging and those with blue shading are being submerged.

Chicago at the very south end of Lake Michigan is submerging at a rate of about cm / century while Tobermory is emerging at a similar rate. (Source Davidson- Arnott from data in Tushingham, A.M., 1992. Postglacial uplift predictions and historical water levels of the Great Lakes. Journal of Great Lakes Research, 18, 440-455)