BOREHOLE DATA AND CLIMATE RECONSTRUCTION IN KOREA

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BOREHOLE DATA AND CLIMATE RECONSTRUCTION IN KOREA
Yasukuni OKUBO1, Hyoung-Chan KIM2, Youhei
UCHIDA3, Shusaku GOTO4 and Jan SAFANDA5 1
Geological Survey of Japan, AIST,
yasu-okubo_at_aist.go.jp 2 Korea Institute of
Geoscience and Mineral Resources,
khc_at_kigam.re.kr 3 Geological Survey of Japan,
AIST, uchida-y_at_aist.go.jp 4Aso Volcanological
Laboratory, Kyoto University, sgoto_at_aso.vgs.kyoto-
u.ac.jp 5Geophysical Institute of Czech Republic,
jsa_at_ig.cas.cz
This is a global perspective of surface
temperature change over the last five centuries,
averaged from 863 individual reconstructions.
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Heat flow densities on the geological map of
Korea (GSJ and KIGAM, 2002).
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Examples of measurements
Deep enough
Old enough Not over-flowing
Important Litho. T-dif.
Hydrodynamic free
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Location of boreholes(?) and meteoric
stations(?).
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Temperature depth data of Seoul
Crystalline rock
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Temperature depth data of Gapyung
Sedimentary rock
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Temperature depth data of Ulsan
Sedimentary rock
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Inversion
(T - T0 ) / (Ts - T0 ) erfc z / ( 2 ( k t )
1/2 )
?ti is time step ?Ti is temperature difference
between ?ti - ?tI 1 G is geothermal
gradient Unknown parameters in the inversion are
T0 , ?Ti , G, k , which are independent of
depth. The time step is fixed to be 5 years in
this case.
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Reconstructed surface temperature and
Reconstructed borehole temperaturein Seoul
lt90 m
90-140 m
1700-1800AD
mid-20th
gt150 m
Red curve indicates the reconstructed surface
temperature. Two blue lines show the range of
standard deviation 1?. Black fluctuating lines
denote observed surface temperatures.
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Reconstructed surface temperature and
Reconstructed borehole temperaturein Gapyung
lt80 m
mid-20th
50-200 m
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Reconstructed surface temperature and
Reconstructed borehole temperaturein Ulsan
50-110 m
mid-20th
Till 1900AD
110-320 m
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DISCUSSION 1
Surface temperature increase over the last 50
years.
Result of Seoul could reflect urbanization.
Hydrodynamic perturbation disturbs a conductive
and steady state thermal regime at the shallow
depth.
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DISCUSSION 2
Unknown thermal diffusivity sometimes produces a
misinterpretation.
New data acquisition near the meteoric station to
confirm the amplitude of temperature increase is
necessary.
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CONCLUSIONS 1 
Korea is a vacant area for the surface
temperature reconstruction from borehole data.
The observed temperature data often include the
hydrodynamic perturbation.
Reconstructed GST series are concordant with the
observed GST.
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CONCLUSIONS 2 
Surface T increases over the last 50 years.
The result in Seoul could reflect urbanization
effect.
To confirm these results, new data acquisition
and reconstruction are necessary.