Heat flow variations in 2 km deep borehole Litoměřice, Czechia

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F67985530%3A_____%2F23%3A00570575" target="_blank" >RIV/67985530:_____/23:00570575 - isvavai.cz</a>

Výsledek na webu

<a href="https://www.sciencedirect.com/science/article/pii/S0375650523000627" target="_blank" >https://www.sciencedirect.com/science/article/pii/S0375650523000627</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.geothermics.2023.102708" target="_blank" >10.1016/j.geothermics.2023.102708</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Heat flow variations in 2 km deep borehole Litoměřice, Czechia

Popis výsledku v původním jazyce

Temperature in 2 km deep borehole Litoměřice, drilled in 2007, was repeatedly logged down to 1700 m in the period 2007 – 2020. We were able to monitor a return of the temperature to the equilibrium temperature-depth profile undisturbed by drilling. The uppermost part of the profile contains signal of the recent warming manifested by a negative temperature gradient close to the surface and a temperature minimum at a depth of about 40 m. The minimum has been migrating downward at a rate of 1.5 – 2 m per year in the period 2015 – 2020. A detailed knowledge of temperature gradient together with thermal conductivity, diffusivity and heat production measurements on the drill-core samples of mica-schist that occurs below 900 m depth enabled us to analyze the heat flow vertical variations in the lithologically homogeneous depth section 900 – 1700 m. We came to the conclusion that temperature-depth profile in this section contains a robust climate signal of the last glacial cycle. The reconstructed ground surface temperature history indicates the magnitude of the last glacial – Holocene warming 13 -15 K and existence of a minimum 15 – 20 ka. The long-term mean ground surface temperature +1 - +2 °C suggests that the borehole site was permafrost free for most of the glacial cycle. Existence of about 100 m deep permafrost is possible in the coldest part of the last glacial. The steady-state surface heat flow has been estimated at 88 mW/m2. The reconstructed ground surface temperature history used as a surface forcing function in a numerical solution of the transient heat conduction equation provided an estimate of the present-day heat flow in the well. The estimate is practically independent from the poorly constrained conductivity of the 900 m thick sedimentary cover. According to it the present-day heat flow is lower than the steady-state one by 20 - 30 mW/m2 in the first hundreds of meters below the surface and still by about 10 mW/m2 at a depth of 1 km.

Název v anglickém jazyce

Heat flow variations in 2 km deep borehole Litoměřice, Czechia

Popis výsledku anglicky

Temperature in 2 km deep borehole Litoměřice, drilled in 2007, was repeatedly logged down to 1700 m in the period 2007 – 2020. We were able to monitor a return of the temperature to the equilibrium temperature-depth profile undisturbed by drilling. The uppermost part of the profile contains signal of the recent warming manifested by a negative temperature gradient close to the surface and a temperature minimum at a depth of about 40 m. The minimum has been migrating downward at a rate of 1.5 – 2 m per year in the period 2015 – 2020. A detailed knowledge of temperature gradient together with thermal conductivity, diffusivity and heat production measurements on the drill-core samples of mica-schist that occurs below 900 m depth enabled us to analyze the heat flow vertical variations in the lithologically homogeneous depth section 900 – 1700 m. We came to the conclusion that temperature-depth profile in this section contains a robust climate signal of the last glacial cycle. The reconstructed ground surface temperature history indicates the magnitude of the last glacial – Holocene warming 13 -15 K and existence of a minimum 15 – 20 ka. The long-term mean ground surface temperature +1 - +2 °C suggests that the borehole site was permafrost free for most of the glacial cycle. Existence of about 100 m deep permafrost is possible in the coldest part of the last glacial. The steady-state surface heat flow has been estimated at 88 mW/m2. The reconstructed ground surface temperature history used as a surface forcing function in a numerical solution of the transient heat conduction equation provided an estimate of the present-day heat flow in the well. The estimate is practically independent from the poorly constrained conductivity of the 900 m thick sedimentary cover. According to it the present-day heat flow is lower than the steady-state one by 20 - 30 mW/m2 in the first hundreds of meters below the surface and still by about 10 mW/m2 at a depth of 1 km.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10507 - Volcanology

Projekt

<a href="/cs/project/GA21-23196S" target="_blank" >GA21-23196S: Rozšíření, mocnost a vývoj permafrostu ve střední Evropě v pozdním kvartéru</a><br>

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2023

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Geothermics

ISSN

0375-6505

e-ISSN

1879-3576

Svazek periodika

111

Číslo periodika v rámci svazku

June

Stát vydavatele periodika

GB - Spojené království Velké Británie a Severního Irska

Počet stran výsledku

11

Strana od-do

102708

Kód UT WoS článku

000959610700001

EID výsledku v databázi Scopus

2-s2.0-85150457260