Long-Term Climate Change: Advances in Understanding Relevant to a Deep Geologic Repository

Abstract

For the past million years of Earth history, the Canadian Shield has experienced a continuous process of glaciation and deglaciation, events that have significantly altered the landscape of the northern half of the North American continent. This sequence of events, ultimately due to small changes in received solar radiation due to the influence of gravitational many body effects upon the earths orbit around the sun, should they continue, constitute an important phenomena with respect to developing an understanding of groundwater flow system evolution in Shield terrain as it may influence the long-term performance of a Deep Geologic Repository for used nuclear fuel. In this paper a description is provided of the University of Toronto Glacial Systems Model, which is being applied to yield geophysically constrained predictions of the last Laurentide (North American) glacial event. In particular, the GSM is providing unique insight into the time rate of change, magnitude and uncertainty of surface boundary conditions and permafrost occurrence at a hypothetical Shield repository site. These predictive estimates of boreal, periglacial and ice-sheet history are offering an innovative and reasoned basis to explore flow system characteristics and attributes that govern hydrodynamic and geochemical stability within deepseated Shield flow domains.