BOREHOLE DATA AND CLIMATE RECONSTRUCTION IN KOREA

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@aist.go.jp

2 Korea Institute of Geoscience and Mineral Resources, khc@kigam.re.kr3 Geological Survey of Japan, AIST, uchida-y@aist.go.jp

4Aso Volcanological Laboratory, Kyoto University, sgoto@aso.vgs.kyoto-u.ac.jp5Geophysical Institute of Czech Republic, jsa@ig.cas.cz

This is a global perspective of surface temperature change over the last five centuries, averaged from 863 individual reconstructions.

Heat flow densities on the geological map of Korea (GSJ and KIGAM, 2002).

Examples of measurements

Deep enoughOld enough Not over-flowing

Important Litho. T-dif.

Hydrodynamic free

Location of boreholes(●) and meteoric stations(▲). 128127 129 130 13112639

38

37

36

35

34

33 126 127 128 129 130 13133

34

35

36

37

38

39

SeoulGapyung

Ulsan

0 50 100 150 200

Synoptic station

Borehole

km

0

100

200

300

400

500

600

700

800

900

1000

Dep

th(m

)

Seoul, KOREA (02000002)

Temperature(oC)

1 0 1 5 2 0 2 5 3 0 3 5 4 0

Long. 127.0249639Lat. 37.488575

Cry

stal

lin

e ro

ck

Temperature – depth data of Seoul

0

100

200

300

400

500

600

700

800

900

1000

Dep

th(m

)

Gapyung, KOREA (03560010)

Temperature(oC)

1 0 1 5 2 0 2 5 3 0 3 5 4 0

Long. 127.5118889Lat. 37.7549111

Temperature – depth data of GapyungS

edim

enta

ry r

ock

0

100

200

300

400

500

600

700

800

900

1000

Dep

th(m

)

Ulsan, KOREA (05220003)

Temperature(oC)

1 0 1 5 2 0 2 5 3 0 3 5 4 0

Long. 129.2846944Lat. 35.4115278

Temperature – depth data of Ulsan S

edim

enta

ry r

ock

Inversion

T (z,t i;T0,Ti ,G , ) T0 G z Ti erfcz

2 ti

erfc

z

2 t i1

i

ti is time stepTi 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.

(T - T0 ) / (Ts - T0 ) = erfc [ z / ( 2 ( k t ) 1/2 ) ]

Reconstructed surface temperature and Reconstructed borehole temperature

in Seoul

>150 m

90-140 m

1700-1800AD

mid-20th

<90 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.

Reconstructed surface temperature and Reconstructed borehole temperature

in Gapyung

50-200 m

mid-20th

<80 m

Reconstructed surface temperature and Reconstructed borehole temperature

in Ulsan

110-320 m

50-110 m

Till 1900AD

mid-20th

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.

New data acquisition near the meteoric station to confirm the amplitude of temperature increase is necessary.

DISCUSSION 2

Unknown thermal diffusivity sometimes produces a misinterpretation.

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.

The result in Seoul could reflect urbanization effect.

To confirm these results, new data acquisition and reconstruction are necessary.

CONCLUSIONS 2 

Surface T increases over the last 50 years.