Last century climate change in Kamchatka, evidence from the underground

We present first results of the geothermal part of the Japanese/Czech/Russian joint three-year project "Reconstruction of the climatic changes from borehole temperature profiles and tree rings in the Kamchatka Peninsula" (2000-2002) adopted by Japan Society for the Promotion of Science (JSPS). To put forward such reconstruction precise temperature measurements were performed in boreholes drilled more than 15-25 years ago. Altogether 33 records of repeated temperature-depth profiles from 10 holes (one up to six logs per hole) to the depth of 400 metres were inverted to construct a climate model of the last 100-150 years. Observed temperature gradients varied in a broad interval of 10 to 60 mK/m and in some holes, regardless of long equilibrium time, certain small variations in the subsurface temperatures due to advective heat transport by underground water were detected. Our data were complemented by 17 old temperature profiles recorded in the area in the early 1980s for heat flow determinations. Regardless of certain diversity of the individual borehole sites and different quality and calibration of old and new data, the results of reconstruction confirmed a general warming of about 1 to 1.5 degree C characteristic of the last century. This warming followed after an inexpressive cooler period typical for the end of the 19th century. In the last three/four decades the warming rate has been increasing up to 0.02 K/year. The results are in good agreement with the surface air temperature data of the last 150 years combining land and marine observations and averaged in the 5x5 degree grid boxes (Jones et al., 1999) and air temperature time-series recorded in a number of local meteorological stations in period 1960-1995. The role of slowly migrating water on the temperature field was further studied by yearlong temperature monitoring at several selected depth levels, which clearly confirmed temperature oscillations with amplitudes of 20 to 30 mK but not affecting the underground climate "signature".