Thermal Effectiveness of a New Type of Air Convection Embankment to Preserve a Northern Airstrip near the Hudson Bay Coast, Canada

Since the 1990s, an obvious increase in mean annual air temperature has been recorded in Nunavik, Quebec. This has resulted in the degradation of permafrost, threatening the stability of airstrip infrastructure managed by Transport Quebec. The air convection embankment (ACE) on side slopes with additional crushed rocks on the natural ground provides one option to preserve permafrost around the toe of embankments where permafrost degradation usually first occurs. To test the combined thermal effectiveness, this protection technique was used at the Puvirnituq airstrip in Nunavik, Quebec, in the summer of 2009. Thermistor strings were installed under the ACE layer to monitor the annual variation of ground temperatures near the toe of the embankment. The measured data indicate cooling trends at the ACE layer/natural ground interface, and the rise of the permafrost ceiling was observed. A numerical model based on site-specific conditions was developed to reproduce subsurface thermal regime and evaluate long-term climate warming effects. The model was calibrated using ground temperature measurements collected between 2010 and 2015. Numerical results indicate that the new type of ACE produces thermal cooling benefits as well as shifts the worst degradation location away from the embankment toe. This study provides a new design option for the ACEs to preserve warming airstrip infrastructures, and this design should be considered for other airstrip infrastructures in Nunavik, Quebec.