Signature of climate changes in subsurface temperatures. A case study from Northern Bohemia, Czechia
A 1.7 km long equilibrium temperature log from borehole Litoměřice, Czechia, measured 13 years after drilling provided a detailed knowledge of temperature gradient. Its most conspicuous feature is a gradual increase with depth from 22.0 K/km to 25.6 K/km within a lithologically homogeneous depth sec...
Main Authors: | , , , |
---|---|
Format: | Conference Object |
Language: | English |
Published: |
2023
|
Subjects: | |
Online Access: | https://gfzpublic.gfz-potsdam.de/pubman/item/item_5018071 |
id |
ftgfzpotsdam:oai:gfzpublic.gfz-potsdam.de:item_5018071 |
---|---|
record_format |
openpolar |
spelling |
ftgfzpotsdam:oai:gfzpublic.gfz-potsdam.de:item_5018071 2023-10-09T21:55:11+02:00 Signature of climate changes in subsurface temperatures. A case study from Northern Bohemia, Czechia Safanda, J. Dědeček, P. Čermák, V. Uxa, T. 2023 https://gfzpublic.gfz-potsdam.de/pubman/item/item_5018071 eng eng info:eu-repo/semantics/altIdentifier/doi/10.57757/IUGG23-1561 https://gfzpublic.gfz-potsdam.de/pubman/item/item_5018071 XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG) info:eu-repo/semantics/conferenceObject 2023 ftgfzpotsdam https://doi.org/10.57757/IUGG23-1561 2023-09-10T23:43:22Z A 1.7 km long equilibrium temperature log from borehole Litoměřice, Czechia, measured 13 years after drilling provided a detailed knowledge of temperature gradient. Its most conspicuous feature is a gradual increase with depth from 22.0 K/km to 25.6 K/km within a lithologically homogeneous depth section 900–1700 m occupied by mica-schist. Conductivity and diffusivity was measured on drill-core samples from the upper part of this borehole section. Due to (i) the homogeneous lithology of mica-schist, (ii) a small scatter of the measured conductivity values and (iii) no trend in the dip angle of foliation, we assumed no depth trend of conductivity in the section 900–1700 m other than that resulting from pressure-temperature corrections. However, they introduce only a slight trend with values decreasing from 3.34 W/(m.K) at 900 m to 3.29 W/(m.K) at 1700 m, i.e. about 1.5 %, that cannot explain the observed 16% increase of the temperature gradient. We interpreted the increase as a transient feature generated by long-term ground surface temperature changes during the last glacial cycle. The inversion technique applied to the temperature log section 900–1700 m indicated the magnitude of the last glacial–Holocene warming of 13–15 K and the occurrence of a temperature minimum 15–20 ka. The long-term mean ground surface temperature of 1–2 °C suggests that the borehole site was permafrost-free for most of the last glacial cycle. The existence of about 100 m deep permafrost is possible in the coldest part of the last glacial. Conference Object permafrost GFZpublic (German Research Centre for Geosciences, Helmholtz-Zentrum Potsdam) |
institution |
Open Polar |
collection |
GFZpublic (German Research Centre for Geosciences, Helmholtz-Zentrum Potsdam) |
op_collection_id |
ftgfzpotsdam |
language |
English |
description |
A 1.7 km long equilibrium temperature log from borehole Litoměřice, Czechia, measured 13 years after drilling provided a detailed knowledge of temperature gradient. Its most conspicuous feature is a gradual increase with depth from 22.0 K/km to 25.6 K/km within a lithologically homogeneous depth section 900–1700 m occupied by mica-schist. Conductivity and diffusivity was measured on drill-core samples from the upper part of this borehole section. Due to (i) the homogeneous lithology of mica-schist, (ii) a small scatter of the measured conductivity values and (iii) no trend in the dip angle of foliation, we assumed no depth trend of conductivity in the section 900–1700 m other than that resulting from pressure-temperature corrections. However, they introduce only a slight trend with values decreasing from 3.34 W/(m.K) at 900 m to 3.29 W/(m.K) at 1700 m, i.e. about 1.5 %, that cannot explain the observed 16% increase of the temperature gradient. We interpreted the increase as a transient feature generated by long-term ground surface temperature changes during the last glacial cycle. The inversion technique applied to the temperature log section 900–1700 m indicated the magnitude of the last glacial–Holocene warming of 13–15 K and the occurrence of a temperature minimum 15–20 ka. The long-term mean ground surface temperature of 1–2 °C suggests that the borehole site was permafrost-free for most of the last glacial cycle. The existence of about 100 m deep permafrost is possible in the coldest part of the last glacial. |
format |
Conference Object |
author |
Safanda, J. Dědeček, P. Čermák, V. Uxa, T. |
spellingShingle |
Safanda, J. Dědeček, P. Čermák, V. Uxa, T. Signature of climate changes in subsurface temperatures. A case study from Northern Bohemia, Czechia |
author_facet |
Safanda, J. Dědeček, P. Čermák, V. Uxa, T. |
author_sort |
Safanda, J. |
title |
Signature of climate changes in subsurface temperatures. A case study from Northern Bohemia, Czechia |
title_short |
Signature of climate changes in subsurface temperatures. A case study from Northern Bohemia, Czechia |
title_full |
Signature of climate changes in subsurface temperatures. A case study from Northern Bohemia, Czechia |
title_fullStr |
Signature of climate changes in subsurface temperatures. A case study from Northern Bohemia, Czechia |
title_full_unstemmed |
Signature of climate changes in subsurface temperatures. A case study from Northern Bohemia, Czechia |
title_sort |
signature of climate changes in subsurface temperatures. a case study from northern bohemia, czechia |
publishDate |
2023 |
url |
https://gfzpublic.gfz-potsdam.de/pubman/item/item_5018071 |
genre |
permafrost |
genre_facet |
permafrost |
op_source |
XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG) |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.57757/IUGG23-1561 https://gfzpublic.gfz-potsdam.de/pubman/item/item_5018071 |
op_doi |
https://doi.org/10.57757/IUGG23-1561 |
_version_ |
1779319021184745472 |