On the Use of Geothermal Data to Study Paleoclimate in Azerbaijan

The geothermal data used for this study consist of high quality borehole temperature-depth profiles at Kura depression in Azerbaijan. Three boreholes located near Sheki (Gamigaya 14), Mingecevir (Garaja 16) and Dalimammadli (Dalimammadli 201) were logged in 1979 /1980. Borehole temperatures were measured more than one year after drilling by thermistor probes of 0.001 degree Celsius sensitivity that were calibrated against a high accuracy (0.01 degree) mercury thermometer. The general calibration curve fitted to the data suggests the temperature accuracy of 0.03 degree. The time constant for the probe is 1 min in water. Measurements were done by lowering the probe slowly to the desired depth and registering temperature after 2-5 minute waiting time. The principal meteorological data used to infer climate change on land are mean annual surface air temperatures (SAT). These measurements are taken approximately 1.5 m above the ground surface. A ground surface temperature history is selected that best explains the observed subsurface perturbation. Alternatively, the surface temperature history can be inferred directly by borehole temperature data inversion. Inversions of temperature data for Garaja-16 and Gamigaya 14 boreholes show the climate warming on 1-2 degree in the past two centuries.