USGS Borehole Temperature Logs from Arctic Alaska, pre-1989
Data Collection Methods
The methods utilized by the U.S. Geological Survey to measure subsurface
temperatures have evolved considerably over the years. Although some of
the early
measurements were obtained using thermistor strings frozen into permafrost, the
vast majority of the measurements were made in fluid-filled holes using a
custom
temperature sensor. A typical sensor used in Alaska prior to 1989
consisted of a
series-parallel network of 20 thermistors; see Sass et al. [1971] for a more
detailed description. During a logging experiment, the resistance of the
thermistor network was determined using a Wheatstone bridge prior to 1967.
After
that time, a 4-wire resistance measurement was made using a commercial
5.5-digit
multimeter (DMM). Before 1984, boreholes were logged in the "incremental" or
"stop-and-go" modes; the vertical spacing of the measurements was typically
3-15
m. Beginning in 1984, the depth/resistance measurements were automatically
stored on magnetic tape, allowing boreholes to be logged in the "continuous"
mode; the typical data spacing for the continuous temperature logs was 0.3 m
(1 ft). Many of the Alaskan boreholes were relogged several times to
quantify the
thermal disturbance caused by drilling the holes (see Lachenbruch and Brewer
[1959]). A review of current temperature measuring techniques used by the USGS
in the polar regions is given by Clow et al. [1996].
References:
Clow, G.D., R.W. Saltus, and E.D. Waddington (1996): A new high-precision
borehole-temperature logging system used at GISP2, Greenland, and Taylor Dome,
Antarctica, J. Glaciology, vol. 42, 576-584.
Lachenbruch, A.H. and M.C. Brewer (1959): Dissipation of the temperature effect
of drilling a well in Arctic Alaska, U.S. Geological Survey Bulletin 1083-C,
109 pp.
Sass, J.H., A.H. Lachenbruch, R.J. Munroe, G.W. Greene, and T.H. Moses, Jr.
(1971): "Heat Flow in the Western United States", J. Geophys. Res., vol. 76,
6376-6413.
Return to Alaska Borehole Temps
U.S. Department of the Interior
U.S. Geological Survey
Central Region Global Change and Climate History Team
This page is <URL: http://esp.cr.usgs.gov/data/bht/alaska/methods.html>
Maintained by Randy Schumann
Wednesday, 15-Mar-2006 14:35:15 MST