TWO-DIMENSIONAL NUMERICAL MODELING OF AN ONTARIO LOBE FLOW LINE DURING THE LAST GLACIAL MAXIMUM

A time-dependent, thermomechanically-coupled, finite-element numerical model previously used to simulate ice sheet and bed interactions along a flow line of the Green Bay Lobe was applied to a flow line of the Ontario Lobe. The model is driven by climate and incorporates geologic and topographic input parameters compiled in a GIS database. The model predicts permafrost distribution and thickness in front of and underneath glacier ice, and accounts for calving and the formation of morainal banks in proglacial lakes. Modifications of the model used in previous studies include the addition of a steeper ice-marginal temperature gradient and an increased east-west precipitation gradient that resulted in greater precipitation along the Ontario Lobe flow line than on the Green Bay Lobe. In the model simulations, these modifications allow the Ontario Lobe to traverse the deep Lake Ontario basin and reach its margin at the time of the Last Glacial Maximum. We also account for proglacial lake-level rise that occurred as ice advance blocked low drainage outlets during advance to the Last Glacial Maximum ice margin position. Results of model simulations also include the development of permafrost beneath ice in the drumlin zone near the Ontario Lobe margin. The results of these model simulations along with previous applications of the model to the Green Bay Lobe demonstrates the usefulness of 2D modeling in understanding the affects of climate and periglacial processes on ice dynamics and hydrology of the lobes of the southern Laurentide Ice Sheet.