Extracting past atmospheric warming and urban heating effects from borehole temperature profiles

Abstract

Borehole temperature logs in urban areas often show deviation from the regional geothermal gradient that increases towards the land surface in the top ~100 meters. This deviation is the sum of two effects: atmospheric global warming and urban heating. To invert the temperature profiles (T-logs), a novel analytical model is presented to distinguish effects of global warming and of urban structures on the ground thermal regime. The inversion is demonstrated on four characteristic T-logs measured in the city and suburbs of Zurich, Switzerland. The logging was performed in borehole heat exchanger U-tubes by an innovative, wireless measuring technique. Detailed information on past climatic and land use changes enabled the focus on two main urban heat sources, buildings and asphalt. For three of the locations, the Tlogs could be reproduced with a plausible heating of the asphalt by 3-3.5 °C, and an average temperature of 15-16 °C below the basement of buildings. However, the other location within the highly urbanized area, is influenced by additional heat sources. In most of the cases, the increased subsurface temperatures and the associated stored additional geothermal energy, mainly originate from urban structures, while climate change is secondary.

The thermal impact of subsurface building structures on urban groundwater resources – A paradigmatic example

“…With this insight, and in the context of climate change, the development of ground thermal regime in urban areas has to be reviewed. This also concerns the understanding of the evolution of SUHI (Arola and Korkka-Niemi, 2014;Bayer et al, 2016;Ferguson and Woodbury, 2004;Huang et al, 2009) and geothermal potentials of the overheated urban subsurface Zhu et al, 2010).…”

Effect of undisturbed ground temperature on the design of closed-loop geothermal systems: A case study in a semi-urban environment

“…Deviations from this distribution can be observed in the case of groundwater flow, varying ground thermal properties and/or anthropogenic effects. The latter results in elevated ground temperatures with zero or negative temperature gradients extending to depths more than 50 m, which is observed worldwide in urban areas [24][25][26][27]. In-situ case studies of temperature borehole logging have revealed increased ground temperatures, which are attributed to the urbanisation effect mainly based on observations of building presence and occupation close to the measurement locations [28][29][30].…”

Surface soil temperatures of various land cover types within the Chianan Plain, southern Taiwan

“…Many of the temperature-depth profiles display a warming trend. Such subsurface temperature distribution may be due to land use change, global warming, or groundwater flow (Kohl 1999;Taniguchi et al 1999Taniguchi et al , 2003Huang et al 2000;Pollack and Huang 2000;Ferguson et al 2006;Bense and Beltrami 2007;Verdoya et al 2007;Kataoka et al 2009;Yamano et al 2009;Bayer et al 2016).…”

“…Temperature-depth profiles are widely used for reconstructing historical surface temperature in association with climate change (Taniguchi et al 1999;Pollack and Huang 2000;Roy et al 2002;Eppelbaum et al 2006;Balobaev et al 2008;Ouzzaouit et al 2014;Bayer et al 2016). Surface soil temperature change can be obtained from PSST minus ISST which is estimated from temperature-depth profile.…”

“…SST is the temperature at the upper boundary of the subsurface temperature-depth profile, an important parameter for understanding subsurface heat transfer (Kupfersberger et al 2017), groundwater recharge (Bense and Beltrami 2007;, soil temperature history, and effects of climate change (Kohl 1998;Balobaev et al 2008;Herb et al 2008;Stevens et al 2008;Bayer et al 2016).…”