Crustal Heat Flow

Beardsmore, Graeme; Cull, J. P.

doi:10.1017/cbo9780511606021

Cited by 254 publications

(88 citation statements)

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“…While the thermal properties of carbonate rocks within karst aquifers can be somewhat variable (Beardsmore and Cull, 2001), uncertainty can be reduced if measured thermal properties for specific formations of interest are available. However, there are still some potential limitations.…”

Section: Limitations Of the Modelmentioning

confidence: 99%

Thermal damping and retardation in karst conduits

Luhmann

Covington²,

Myre³

et al. 2015

Hydrol. Earth Syst. Sci.

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Abstract. Water temperature is a non-conservative tracer in the environment. Variations in recharge temperature are damped and retarded as water moves through an aquifer due to heat exchange between water and rock. However, within karst aquifers, seasonal and short-term fluctuations in recharge temperature are often transmitted over long distances before they are fully damped. Using analytical solutions and numerical simulations, we develop relationships that describe the effect of flow path properties, flow-through time, recharge characteristics, and water and rock physical properties on the damping and retardation of thermal peaks/troughs in karst conduits. Using these relationships, one can estimate the thermal retardation and damping that would occur under given conditions with a given conduit geometry. Ultimately, these relationships can be used with thermal damping and retardation field data to estimate parameters such as conduit diameter. We also examine sets of numerical simulations where we relax some of the assumptions used to develop these relationships, testing the effects of variable diameter, variable velocity, open channels, and recharge shape on thermal damping and retardation to provide some constraints on uncertainty. Finally, we discuss a multitracer experiment that provides some field confirmation of our relationships. High temporal resolution water temperature data are required to obtain sufficient constraints on the magnitude and timing of thermal peaks and troughs in order to take full advantage of water temperature as a tracer.

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Section: Limitations Of the Modelmentioning

confidence: 99%

Thermal damping and retardation in karst conduits

Luhmann

Covington²,

Myre³

et al. 2015

Hydrol. Earth Syst. Sci.

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“…Figure 2b plots the modeled subsurface temperature anomalies associated with the selected basal temperatures as functions of depth. A thermal diffusivity of κ = 10 −6 m 2 s −1 was assumed to be representative of common nonporous crustal rocks (e.g., Drury, 1986;Beardsmore and Cull, 2001;Pasquale et al, 2014). Each of the basal temperature histories cause perturbations within the upper 1000 m of the selected profiles that could obscure the correct estimate of the geothermal gradient ( = No efforts were made to take into account any geological differentiation, vertically or horizontally.…”

Section: Impact Of Postglacial Warming On the Determination Of The Stmentioning

confidence: 99%

Numerical studies on the Impact of the Last Glacial Cycle on recent borehole temperature profiles: implications for terrestrial energy balance

et al. 2014

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Abstract. Reconstructions of past climatic changes from borehole temperature profiles are important independent estimates of temperature histories over the last millennium. There remain, however, multiple uncertainties in the interpretation of these data as climatic indicators and as estimates of the changes in the heat content of the continental subsurface due to long-term climatic change. One of these uncertainties is associated with the often ignored impact of the last glacial cycle (LGC) on the subsurface energy content, and on the estimate of the background quasi steadystate signal associated with the diffusion of accretionary energy from the Earth's interior. Here, we provide the first estimate of the impact of the development of the Laurentide ice sheet on the estimates of energy and temperature reconstructions from measurements of terrestrial borehole temperatures in North America. We use basal temperature values from the data-calibrated Memorial University of Newfoundland glacial systems model (MUN-GSM) to quantify the extent of the perturbation to estimated steady-state temperature profiles, and to derive spatial maps of the expected impacts on measured profiles over North America. Furthermore, we present quantitative estimates of the potential effects of temperature changes during the last glacial cycle on the borehole reconstructions over the last millennium for North America. The range of these possible impacts is estimated using synthetic basal temperatures for a period covering 120 ka to the present day that include the basal temperature history uncertainties from an ensemble of results from the calibrated numerical model. For all the locations, we find that within the depth ranges that are typical for available boreholes (≈ 600 m), the induced perturbations to the steady-state temperature profile are on the order of 10 mW m −2 , decreasing with greater depths. Results indicate that site-specific heat content estimates over North America can differ by as much as 50 %, if the energy contribution of the last glacial cycle in those areas of North America that experienced glaciation is not taken into account when estimating recent subsurface energy changes from borehole temperature data.

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“…Therefore, we need to determine the average compacted conductivity, which is given by the harmonic mean of the individual compacted layers [Beardsmore and Cull, 2001]:…”

Section: Compaction Modelmentioning

confidence: 99%

Apollo lunar heat flow experiment revisited: A critical reassessment of the in situ thermal conductivity determination

Grott¹,

Knollenberg²,

Krause³

2010

J. Geophys. Res.

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[1] Lunar heat flow was determined in situ during the Apollo 15 and 17 missions, but some uncertainty is connected to the value of the regolith's thermal conductivity, which enters as a linear factor into the heat flow calculation. Different approaches to determine the conductivity yielded discordant results, which led to a downward correction of the obtained heat flow values by 30%-50% subsequent to the publication of the first results. We have reinvestigated likely causes for the observed discrepancies and find that neither poor coupling between the probe and regolith nor axial heat loss can explain the obtained results. Rather, regolith compaction and compression likely caused a local increase of the regolith's thermal conductivity by a factor of 2-3 in a region which extends at least 2-5 cm from the borehole wall. We conclude that the corrected lunar heat flow values, which are based on thermal diffusivity estimates sampling a large portion of undisturbed regolith, represent robust results. Future in situ measurements of regolith thermal conductivity using active heating methods should take care to both minimize regolith disturbance during probe emplacement and maximize heating time to obtain reliable results. We find that for the Apollo measurements, heating times should have exceeded at least 100 h, and ideally 200 h.Citation: Grott, M., J. Knollenberg, and C. Krause (2010), Apollo lunar heat flow experiment revisited: A critical reassessment of the in situ thermal conductivity determination,

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Crustal Heat Flow

Cited by 254 publications

References 0 publications

Thermal damping and retardation in karst conduits

Thermal damping and retardation in karst conduits

Numerical studies on the Impact of the Last Glacial Cycle on recent borehole temperature profiles: implications for terrestrial energy balance

Apollo lunar heat flow experiment revisited: A critical reassessment of the in situ thermal conductivity determination

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