HR: 0800h
AN: C51A-0070    [Abstracts]
TI: Ground surface temperature history of the past 50000 years inferred from deep borehole temperature profiles in Canada: implications for conditions at the base of the Laurentide ice sheet.
AU: * Chouinard, C
EM: cchouin@olympus.geotop.uqam.ca
AF: GEOTOP-UQAM-McGill, University of Quebec at Montreal, POB 8888, sta. "downtown", Montreal, QC H3C3P8, Canada
AU: Mareschal, J
EM: mareschal.jean-claude@uqam.ca
AF: GEOTOP-UQAM-McGill, University of Quebec at Montreal, POB 8888, sta. "downtown", Montreal, QC H3C3P8, Canada
AB: Several deep boreholes (>2000m) have been logged for temperature near Sudbury and Manitouwadge in Ontario, Canada. Thermal conductivity and radiogenic heat production measurements were made on core samples from all boreholes. From these temperature depth profiles, the heat production, and the thermal conductivity data, we calculated the perturbations to the steady-state temperature regime. These perturbations are interpreted as caused by past temperature changes at the ground surface. The depth of these holes is sufficient to infer variations in ground surface temperature over the past 20,000-50,000 years (i.e. including the last glacial maximum (LGM)). We have used two different inversion techniques, one based on the singular value decomposition algorithm and the other based on a Monte Carlo search of parameter space to obtain the ground surface temperature history (GSTH) of the past 50,000 years for each site. Both sites show that temperatures at the base of the glacier were only marginally colder (<5K) during the LGM that at present. We compare the ground surface temperature history at these two sites with GSTHs previously inferred from other deep boreholes located in central and eastern Canada. The new results confirm that over most of southern Canada the temperatures at the base of the Laurentide ice sheet during the LGM were everywhere near the melting point of ice, with only weak regional differences.
DE: 0726 Ice sheets
DE: 0764 Energy balance
DE: 8130 Heat generation and transport
SC: Cryosphere [C]
MN: 2007 Fall Meeting