USING GPS, BATHYMETRY, AND LIDAR DATA TO QUANTIFY THE IMPACT OF GLACIAL ISOSTATIC REBOUND ON THE POSITION OF THE LAKE ONTARIO SHORELINE, MONROE COUNTY, NY

Following the Last Glacial Maximum (approximately 18 ka) North America has experienced significant isostatic rebound in response to the loss of glacial ice. Vertical motion of the lithosphere is well documented using a variety of approaches ranging from historical markers to ancient shorelines. GPS data quantify a gradient in uplift rates with the highest rates to the north, where ice was the thickest, and the rate of uplift progressively becoming lower towards the south. The “hinge line” – i.e. the transition from uplift to subsidence – runs through Lake Ontario. The northern shore of Lake Ontario is therefore uplifting, while the southern shore is subsiding. Differential vertical motion of the Lake Ontario basin results in the lake “spilling” towards its southern shore, a result documented by previous studies examining tide gauge data. In this contribution we aim to investigate how the three-dimensional shape of the Lake Ontario basin directs spillover to the south. Integration of a bathymetry dataset from the National Oceanic and Atmospheric Administration (NOAA) with GPS-determine rates of uplift/subsidence allow us to model the changing bathymetry of Lake Ontario. Assuming a constant volume of water in the lake based on the bathymetry and historical lake level data from NOAA, we use this model to quantify the shift of water to towards the southern shore. Lastly, a LiDAR dataset from Monroe County, NY provides an opportunity to visualize the impact of isostatic rebound driven local lake level rise on one portion of the southern shoreline of Lake Ontario.