Laurentide Ice Sheet basal temperatures during the last glacial cycle as inferred from borehole data

Abstract

Abstract. Thirteen temperature-depth profiles ( ≥ 1500 m) measured in boreholes in eastern and central Canada were inverted to determine the ground surface temperature histories during and after the last glacial cycle. The sites are located in the southern part of the region that was covered by the Laurentide Ice Sheet. The inversions yield ground surface temperatures ranging from −1.4 to 3.0 • C throughout the last glacial cycle. These temperatures, near the pressure melting point of ice, allowed basal flow and fast flowing ice streams at the base of the Laurentide Ice Sheet. Despite such conditions, which have been inferred from geomorphological data, the ice sheet persisted throughout the last glacial cycle. Our results suggest some regional trends in basal temperatures with possible control by internal heat flow.

Impacts of the Last Glacial Cycle on ground surface temperature reconstructions over the last millennium

“…Such a step model, by definition, yields a positive temperature anomaly in the subsurface at all times. This ignores the temporally and spatially complex structure of the LGC that is indicated by data [Rolandone et al, 2003;Chouinard and Mareschal, 2009;Pickler et al, 2016] and detailed modeling [Tarasov and Peltier, 2007] of the Laurentide Ice Sheet (e.g., see examples in Figure 2 of Beltrami et al [2015a]).…”

Late Weichselian thermal state at the base of the Scandinavian Ice Sheet

“…There are different opinions about the causes of thawed zones occurrence. Basal temperature is usually related to the value of geothermal heat flow from the Earth's interior (Pickler et al, 2016;MacGregor et al, 2016;Rogozhina et al, 2016). Certainly geothermal heat flow has a part in the formation of glacier thermal state however not crucial.…”

“…Direct estimates of the past basal thermal state of the ice sheet can be obtained by the analysis of modern distribution of rock temperatures measured in deep (1.5 -2 km deep) boreholes (Kukkonen and Safanda, 1996;Kukkonen et al, 1998;2011;Mareschal et al, 1999;Demezhko and Shchapov, 2001;Rolandone et al, 2003;Glasnev et al, 2004;Rath and Mottaghy, 2007;Majorowicz and Šafanda, 2008;Chouinard and Mareschal, 2009;Majorowicz, 2012;Demezhko et al, 2013;Pickler et al, 2016). However, there are only a few such data all over the world.…”

North American regional climate reconstruction from ground surface temperature histories

“…In borehole climatology, two distinct methods can be used to determine the geothermal "quasi" steady state: (1) calculating linear regression of the lowermost 100 m (Beltrami et al, 2011(Beltrami et al, , 2015 and (2) including T 0 and 0 into the parameter vector and solving the system of equations using the full profile (Pickler et al, 2016a). The first method was utilized in this study.…”