Laurentide Ice Sheet Basal Temperatures at the Last Glacial Cycle As Inferred from Borehole Temperature Data

Abstract:

Twelve temperature-depth profiles (>1500 m) located in Eastern to Central Canada were studied to determine the past ground surface temperature histories (GSTH) for the Last Glacial Cycle (LGC) and afterwards. The GSTHs were inferred using singular variable decomposition (SVD). Three locations (Sudbury, Manitouwadge, and Thompson) presented multiple boreholes. Here, simultaneous inversion was utilized to illustrate any regional trends present. For all studied sites, the inversion shows that ground surface temperatures throughout the LGC near the pressure melting point of ice, -1.41-2.51°C. These ground surface temperatures are representative of the basal temperatures of the Laurentide Ice Sheet, which covered the region throughout the LGC. These temperatures allow for the possibility of basal flow and fast flowing ice streams, which have been inferred from geomorphological data and are consistent with modeling efforts. Regional variations in basal temperatures are observed. These could be attributed to fluctuations in ice sheet thickness and proximity to the edge of the ice sheet. No correlation between heat flow and the amplitude of the GSTH variations was observed, leading to the conclusion that the basal temperatures in this region are primarily driven by ice dynamics.