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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy (S) - IASPEI - International Association of Seismology and Physics of the Earth's Interior JSS017 Poster presentation 2385 Temperature-time series, thermal regime and the instability of the fluid column in a borehole Dr. Vladimir Cermak Geophysical Institute Academy of Sciences of the Czech Republic IASPEI The increase in sensitivity together with extended data storage capacity of data loggers has opened new horizons for detailed in-situ borehole experiments. Observational evidence proved that even when a borehole is in apparently well stabilized conditions, temperature data may exhibit certain unrest resembling irregular oscillations. (1) We demonstrate the results of monitoring experiments performed in widely different geological settings: incidental observations from Kamchatka, Finland and Mexico together with systematic studies performed in the test hole in Prague (Czech Rep.) covering time span of various length (days to months) with sampling interval varying from seconds to minutes. (2) Temperature in the borehole fluid (water) exhibits oscillation of the order of several thousandths or even hundredths of degree. (3) The character of the oscillation may differ depth to depth and (probably) also time to time. (4) Obtained temperature-time series displayed intermittent, non-periodic oscillations of temperature with sharp gradients and large fluctuations over all observed time scales. (5) Local growth of the second moment technique revealed the presence of at least two distinct temperature forming processes. One of them can be related to heat transfer in the structurally and compositionally complex subsurface. The second of them, which presents the bulk of the measured signal, probably reflects intra-hole convection. It can be demonstrated that at higher Rayleigh numbers the periodic character of oscillations characteristic for quiescent regime is superseded by stochastic features. The oscillatory convection occurs due to instability of the horizontal boundary layers. In spite of the fact that convection is characterized by slow motion, the oscillatory intra-hole flow and corresponding temperature patterns may exhibit features typical of turbulence. The synchronous arrangement of several data loggers (up to five) located at close depth intervals (a few meters) enabled to map time variation of the local temperature patterns at depth. Keywords: borehole temperature, convection, temperature time monitoring
IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy (S) - IASPEI - International Association of Seismology and Physics of the Earth's Interior JSS017 Poster presentation 2386 Resolving terrain effects in borehole temperature profiles Mrs. Shannon Heinle Geology and Geological Engineering University of North Dakota IASPEI William Gosnold Reliable borehole temperature profiles are critical for paleoclimate analysis. As many climate workers have discovered, T-z profiles in boreholes can contain a variety of steady-state and transient nonclimate-related signals. These noise signals include terrain effects such as, topography, land use, land cover, direct and diffused sun radiation, slope angle, and dynamic elements such as groundwater flow and variable precipitation, wind, and snow cover. Few of these effects can be quantified and therefore it is difficult to apply corrections to profiles. However, several studies have concluded that topographical effects, which exert the largest influence on temperature profiles, may be modeled with some degree of confidence. We are attempting to determine the specific terrain effects affecting borehole temperature profiles in the 130 United States boreholes included in the IHFC borehole paleoclimate data set and to determine the feasibility of correcting terrain effects on these boreholes. We are using a combination of remote sensing and field site visits in our analysis. Temperature profiles we have studied have shown promise in categorizing terrain effects. Keywords: terrain effect, borehole, climate
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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy<br />
(S) - <strong>IASPEI</strong> - International Association of Seismology and Physics of the Earth's<br />
Interior<br />
JSS017 Poster presentation 2385<br />
Temperature-time series, thermal regime and the instability of the fluid<br />
column in a borehole<br />
Dr. Vladimir Cermak<br />
Geophysical Institute Academy of Sciences of the Czech Republic <strong>IASPEI</strong><br />
The increase in sensitivity together with extended data storage capacity of data loggers has opened<br />
new horizons for detailed in-situ borehole experiments. Observational evidence proved that even when<br />
a borehole is in apparently well stabilized conditions, temperature data may exhibit certain unrest<br />
resembling irregular oscillations. (1) We demonstrate the results of monitoring experiments performed<br />
in widely different geological settings: incidental observations from Kamchatka, Finland and Mexico<br />
together with systematic studies performed in the test hole in Prague (Czech Rep.) covering time span<br />
of various length (days to months) with sampling interval varying from seconds to minutes. (2)<br />
Temperature in the borehole fluid (water) exhibits oscillation of the order of several thousandths or<br />
even hundredths of degree. (3) The character of the oscillation may differ depth to depth and<br />
(probably) also time to time. (4) Obtained temperature-time series displayed intermittent, non-periodic<br />
oscillations of temperature with sharp gradients and large fluctuations over all observed time scales. (5)<br />
Local growth of the second moment technique revealed the presence of at least two distinct<br />
temperature forming processes. One of them can be related to heat transfer in the structurally and<br />
compositionally complex subsurface. The second of them, which presents the bulk of the measured<br />
signal, probably reflects intra-hole convection. It can be demonstrated that at higher Rayleigh numbers<br />
the periodic character of oscillations characteristic for quiescent regime is superseded by stochastic<br />
features. The oscillatory convection occurs due to instability of the horizontal boundary layers. In spite<br />
of the fact that convection is characterized by slow motion, the oscillatory intra-hole flow and<br />
corresponding temperature patterns may exhibit features typical of turbulence. The synchronous<br />
arrangement of several data loggers (up to five) located at close depth intervals (a few meters) enabled<br />
to map time variation of the local temperature patterns at depth.<br />
Keywords: borehole temperature, convection, temperature time monitoring