Effect of postglacial warming seen in high precision temperature log deep into the granites in NE Alberta

Abstract

The method how to reconstruct surface temperature history from inversions of precise temperature logs done in wells was pioneered earlier by Cermak (1971) and by Lachenbruch and Marshall (1986); (see: Bodri and Cermak 2007 for review and list of references on the subject). The method is based on the inversion of stabilized, high precision deep borehole temperature logs, which are in thermal equilibrium with surrounding rock. Deep down to some 2-km depth perturbation of the heat flow could be caused by warming since recent glaciations ending some 12–13 kyr ago in Canada (Ritchie 1983). Surface temperatures peaked in the Holocene Optimum 6–7 kyr ago known to be some 1–2 °C warmer than recent centuries temperature level (Kerwin et al. 1999). Perturbations observed down to 0.1–0.3 km are mainly related to the climate changes of the last 1–2 centuries (Pollack et al. 1998; Bodri and Cermak 2007; Rath et al. 2012) on large regional and continental scale. All these surface temperature changes influence the subsurface heat flow. The method has been applied to reconstruct timing and amplitude of surface temperature change from latest glacial to postglacial climatic history through many areas in Eurasia and North America (Hotchkiss and Ingersoll 1934; Cermak 1971; Kukkonen 1993; Kukkonen and Safanda 1996; Kukkonen et al. 1998; Mareschal et al.1999; Rolandon et al. 2003; Kukkonen and Joeleht 2003; Demezhko et al. 2007; Demezhko and Golovanova 2007; Majorowicz