NUMERICAL SIMULATIONS OF COUPLED GROUNDWATER FLOW AND HEAT TRANSPORT INCORPORATING FREEZE/THAW CYCLES AND PHASE CHANGE IN A CONTINUOUS PERMAFROST ENVIRONMENT

Masoumeh Shojae Ghias, René Therrien, John Molson, Jean-Michel Lemieux

In the proceedings of: GeoQuébec 2015: 68th Canadian Geotechnical Conference & 7th Canadian Permafrost Conference

Session: Physical and Numerical Modelling in Cold Regions / Modélisation physique et numérique en régions nordiques

ABSTRACT: This study presents a series of numerical simulations to investigate the factors that control permafrost freezing and thawing in the shallow soil zone of the continuous permafrost environment at the Iqaluit Airport in Nunavut, Canada. A simplified conceptual model is first developed to represent the groundwater flow and thermal regime of the soil column and future climate scenarios are prepared based on those proposed by the IPCC (Intergovernmental Panel on Climate Change). A numerical model is then calibrated against ground temperatures. The calibrated model produced an excellent match with observed data and the mean absolute error is estimated to be 0.64 , which is 1.6% of the maximum temperature range. Numerical simulations reveal that under climate warming, conductive heat transport is the main driver for permafrost degradation at this site and that advective heat transport plays a minor role. This result can be attributed to the thaw front not migrating deeply enough into the ground to allow significant flow to develop and to the significant extent of low-permeability soil close to surface, which decreases the rate of flow and reduces the possible effects of thaw driven by advection.

RÉSUMÉ: Cette étude présente les résultats de simulations numériques utilisées pour identifier les facteurs qui contrôlent les climatiques. Dans un premier temps, le modèle numérique fut calé pour représenter les conditions actuelles du climat iques sur le pergélisol, cette étude évalue également le rôle des processus de transport advectif de la chaleur sur le régime sensiblement les recharge et de ce fait limite le transport advectif de la chaleur.

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