Reconstruction of the surface warming history of western interior Canada from borehole temperature profiles and other climate information

Abstract

Over the past several decades annual surface air temperature (SAT) warming in western interior Canada has been more than twice that of the global average. Inversions of the temperature profiles in boreholes throughout this large region provide evidence of anomalously high ground surface temperature (GST) warming trends between the mid-19th century and present. Previous studies have identified strong SAT/GST associations throughout this region for the 20th century. This analysis of the composite, century-scale, regional GST histories (GSTHs) is based on the deepest available borehole temperature logs from the Foreland Sedimentary Basin in western and northern Canada, east of the Cordillera. Although separated by almost 20° latitude, there is strong regional correlation (r = 0.98) between the GSTHs developed from northern (boreal forest) and southern (prairie grassland) boreholes. When filtered, the GSTHs of western Canada correlate strongly with the northern hemisphere (r = 0.80) and the Canadian Arctic (r = 0.86) high temporal resolution proxy climate histories. Strong correlation also exists between the prairie grassland GSTH curve and the tree-ring-based surface summer temperature history from the Columbia Icefield in the Canadian Rocky Mountains close to Athabasca Glacier (r = 0.95). These findings strongly suggest that the similar, but enhanced, SAT warming signal identified by GSTHs makes western interior Canada a strong indicator region of global warming.