Day Of The Year 1998

Fig. 15. Results of one-year temperature monitoring at several shallow depths in Sporilov hole. The profiles well illustrate the amplitude decrement and phase delay of the temperature change with depth.

are not occasional variations and really represent the result of the long-term processes of changing climate.

This conclusion is supported by repeated temperature logging of borehole Hearst (Canada) that embraces even longer period of time. Three holes together with Hearst site were drilled in northeastern Ontario in 1968 as a part of the heat flow project of the Dominion Observatory. The sites were carefully selected in a relatively flat terrain and in geologically uniform strata. The 600 m deep borehole Hearst is located in a slightly elevated, bushed area at the boundary of large forested and cleared fields. A small nearby lake and swampy area affect the temperatures insignificantly. The first incremental log was measured in 1969 (Cermak and Jessop, 1971). Further virtually continuous loggings were performed in 1985 and in 2000. Temperature measurements are highly precise with absolute accuracy of less than 20 mK for the incremental logs and as small as 10mK for the continuous logs (for further details see Section 2.4.3). Figure 17 compiles the results of these measurements. As seen, all temperature logs are quite coherent with weak, but clear positive "U-shape" curvature in their uppermost parts. Figure 17 and all similar

Fig. 16. Measured (a) and reduced (b) temperature profiles for borehole GC-1, NW Utah, USA. Temperature logging was repeatedly performed in years 1978, 1990, and 1992 (data by Chapman and Harris, 1993). Bottom panel (c) shows the temperature differences between the individual logs (data points) together with the synthetic temperature-difference profile (solid line) computed from the 100-year meteorological record of SATs recorded in the nearby weather station.

Fig. 16. Measured (a) and reduced (b) temperature profiles for borehole GC-1, NW Utah, USA. Temperature logging was repeatedly performed in years 1978, 1990, and 1992 (data by Chapman and Harris, 1993). Bottom panel (c) shows the temperature differences between the individual logs (data points) together with the synthetic temperature-difference profile (solid line) computed from the 100-year meteorological record of SATs recorded in the nearby weather station.

TEMPERATURE, deg.C REDUCED TEMPERATURE, K

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