Climate trends in northern Ontario and Québec from borehole temperature profiles

Abstract. The ground surface temperature histories of the past 500 years were reconstructed at 10 sites containing 18 boreholes in northeastern Canada. The boreholes, between 400 and 800 m deep, are located north of 51° N and west and east of James Bay in northern Ontario and Québec. We find that both sides of James Bay have experienced similar ground surface temperature histories with a warming of 1.51 ± 0.76 K during the period of 1850 to 2000, similar to borehole reconstructions for the southern portion of the Superior Province and in agreement with available proxy data. A cooling period corresponding to the Little Ice Age was found at only one site. Despite permafrost maps locating the sites in a region of discontinuous permafrost, the ground surface temperature histories suggest that the potential for permafrost was minimal to absent over the past 500 years. This could be the result of air surface temperature interpolation used in permafrost models being unsuitable to account for the spatial variability of ground temperatures along with an offset between ground and air surface temperatures due to the snow cover.