NUMERICAL MODELLING OF PERMAFROST-IMPACTED HYDROGEOLOGICAL FLOW SYSTEMS UNDER CLIMATE CHANGE (Invited Presentation)

Permafrost thaw due to climate warming is having significant effects on hydrologic and hydrogeological systems in the north. Changes to ground surface conditions, and increased permeability and recharge due to melting of ground ice, for example, are creating new dynamic flow systems with implications for new water supplies. In addition, positive feedback from increased water infiltration and groundwater flow can accelerate permafrost degradation. Numerical modelling can provide important new insights into these coupled processes and can be used to predict future behavior.

The numerical model HEATFLOW is here applied to simulate two well-characterized field sites in Nunavik (Québec), Canada: one near Umiujaq in the discontinuous permafrost zone where changes in groundwater flow, surface vegetation and development of thermokarst lakes are accelerating permafrost thaw, and the other in Salluit where a river-talik (an unfrozen zone below a river) within a continuous permafrost zone has been simulated in three-dimensions. The simulations include groundwater flow coupled to advective-conductive heat transport with temperature-dependent hydraulic conductivity and thermal properties, as well as freeze-thaw and latent heat. Model spin-up periods on the order of a couple of decades are used to initialize the simulation scenarios with realistic flow velocities and temperatures.

The simulated flow systems and temperature fields help to highlight the complex and dynamic interactions within these field-scale cryo-hydrogeological systems under changing surface boundary conditions. In all cases, advective heat transport by flowing groundwater plays an important role in affecting permafrost dynamics.