30,000 YEARS OF GROUND SURFACE TEMPERATURE AND HEAT FLUX CHANGES IN KARELIA RECONSTRUCTED FROM BOREHOLE TEMPERATURE DATA

Analyses of temperature-depth profiles logged in deep boreholes (> 1 km) permit the reconstruction of ground surface temperature (GST) and surface heat flux (SHF) histories in the period of global climate change at the border of the Pleistocene and the Holocene. We reconstructed past GST and SHF histories using data obtained from the 3.5-km-deep Onega borehole (Karelia, north-west Russia). The resulting reconstructions include information on the basal thermal regime of the Scandinavian Ice Sheet, which covered the region in the Last Glacial Maximum (LGM). The surface temperature history reveals a high amplitude of Pleistocene/ Holocene warming equal to 18–20 K. The heat flux changes precede the surface temperature changes and are close to the variations of insolation at a latitude of 60°N. A comparison of the reconstructed GST and SHF histories with the records of carbon dioxide contents in Antarctic ice cores shows that CO2 changes are much closer to temperature changes than they are to heat flux changes