Warming Permafrost Temperatures at Two Mine Sites in the North Slave Region, Northwest Territories, Canada

摘要

Geotechnical investigations conducted by EBA, a Tetra Tech Company, at two proposed mine sites (Tyhee and NICO) in the Canadian Northwest Territories have revealed warming trends in permafrost temperatures. Very warm, locally ice-rich, discontinuous permafrost with ground temperatures ranging from 0.0° to -0.6°C at the depth of zero annual amplitude was identified at the Tyhee site. The recent Tyhee ground temperature data indicate a warming trend with an increase of up to 0.2°C in the permafrost temperature since 2007. At the NICO site, warm discontinuous permafrost was found to be locally ice-rich, with ground temperatures ranging from -1.0°C to -1.8°C at the depth of zero annual amplitude. An increase of up to 0.6°C in the permafrost temperature has been observed at the NICO site since 2004. Permafrost distribution mapping at these two sites was carried out using Ikonos satellite imagery, borehole and testpit logs, and ground temperature monitoring data. The delineated areas of sensitive permafrost terrain were avoided during mine infrastructure siting.