NUMERICAL SIMULATION OF COUPLED GROUNDWATER FLOW AND HEAT TRANSPORT IN A CONTINUOUS PERMAFROST ENVIRONMENT

Ongoing field investigations at the Iqaluit airport in Nunavut, Canada, aim at investigating factors that control freezing and thawing cycles of permafrost that in turn cause degradation of existing runways, taxiways, aprons and access roads. Iqaluit is located in the south-eastern part of Baffin Island at the head of Frobisher Bay, at a latitude of 63º45’ N. The airport is constructed on a flat terrain located above a succession of glacial deposits and surrounded by hills and rocky plateaus of the Precambrian Shield, in a region of continuous permafrost. Data are currently being collected on soil temperature and movement, surficial geology, snowpack thickness, subsurface hydraulic and thermal properties, as well as water table elevations. The purpose of this work is to identify hydrogeological factors and environmental drivers that have the greatest influence on permafrost degradation at the Iqaluit airport, under future climate scenarios proposed by the IPCC. Based on the current hydrogeological conceptual model at the Iqaluit airport, numerical simulations of coupled groundwater flow and heat transport have been designed to test the impact of plausible combinations of hydrogeological parameters and surface conditions on the temporal and spatial evolution of permafrost degradation. A series of simulations have been designed based on current conditions at the Iqaluit airport, which are assumed to be representative of cold-region paved terrains. The scenarios considered here include: the effect of soil compaction and consolidation on surface material, such as paved roads or natural ground surface, the influence of snow cover, heterogeneity of subsurface glacial deposits including ice lenses, anisotropic hydraulic and thermal properties, and the role of recharge and ground water flow on ground temperature distribution including the relative effect of advective versus conductive heat transport. The results of the various simulations will help enhance the understanding of the interactions between the physical/thermal processes and feedback between frozen ground and different hydrogeological environments, which are of concern for hydrogeological studies in high-latitude areas.