Postglacial Time Calculations from Recent Geothermal Measurements in the Calumet Copper Mines

Hotchkiss, W. O.; Inǵersoll, L. R.

doi:10.1086/624142

Cited by 52 publications

(25 citation statements)

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“…2.2). The thermal effects of the LGC have been discussed previously as sources of bias in estimates of this background steady-state signal (e.g., Hotchkiss and Ingersoll, 1934;Jessop, 1971), but recent results have more quantitatively characterized the important impact of the LGC on BTP interpretations (Rath et al, 2012). Though known to be significant for a long time, LGC effects on heat flow density estimations have only recently been characterized in appropriate detail within general geothermal studies (e.g., Slagstad et al, 2009;Majorowicz and Wybraniec, 2011;Westaway and Younger, 2013).…”

Section: H Beltrami Et Al: Glacial Cycle Impactmentioning

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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Section: H Beltrami Et Al: Glacial Cycle Impactmentioning

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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“…Persistent temporal changes in the ground surface energy balance cause variations of the ground temperature that diffuse downwards and are recorded as temperature anomalies superimposed on the linear steady-state geotherm (e.g. Hotchkiss and Ingersoll, 1934;Birch, 1948;Beck, 1977). The extent to which the ground surface temperature changes are recorded is proportional to their duration and amplitude and inversely proportional to the time when they occurred.…”

Section: Introductionmentioning

confidence: 99%

“…The first attempt to infer climate history from temperature-depth profiles was the study by Hotchkiss and Ingersoll (1934), who estimated the timing of the ice retreat at the end of the last glaciation. It was, however, not until the 1970s that systematic studies were undertaken to infer past climate from such profiles (e.g.…”

Section: Introductionmentioning

confidence: 99%

Climate trends in northern Ontario and Québec from borehole temperature profiles

2016

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Abstract. The ground surface temperature histories of the past 500 years were reconstructed at 10 sites containing 18 boreholes in northeastern Canada. The boreholes, between 400 and 800 m deep, are located north of 51 • N and west and east of James Bay in northern Ontario and Québec. We find that both sides of James Bay have experienced similar ground surface temperature histories with a warming of 1.51 ± 0.76 K during the period of 1850 to 2000, similar to borehole reconstructions for the southern portion of the Superior Province and in agreement with available proxy data. A cooling period corresponding to the Little Ice Age was found at only one site. Despite permafrost maps locating the sites in a region of discontinuous permafrost, the ground surface temperature histories suggest that the potential for permafrost was minimal to absent over the past 500 years. This could be the result of air surface temperature interpolation used in permafrost models being unsuitable to account for the spatial variability of ground temperatures along with an offset between ground and air surface temperatures due to the snow cover.

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“…If there are no temporal changes in GST, subsurface temperature increases linearly with depth. When persistent temporal GST variations occur, they diffuse downward and are recorded as perturbations to Earth's steady-state geotherm (see, e.g., Hotchkiss and Ingersoll, 1934;Birch, 1948;Beck, 1977). The time of occurrence, duration, and amplitude of GST changes govern the extent to which they are recorded.…”

mentioning

confidence: 99%

“…The time of occurrence, duration, and amplitude of GST changes govern the extent to which they are recorded. Attempts to infer past climate from these borehole temperature-15 depth profiles began in the 1930s (Hotchkiss and Ingersoll, 1934). It was, however, only in the 1970s that systematic studies to infer past climate were undertaken (Cermak, 1971;Sass et al, 1971;Beck, 1977).…”

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confidence: 99%

Recent climate variations in Chile: constraints from borehole temperature profiles

Pickler¹,

Fausto²,

Beltrami³

et al. 2017

Preprint

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Abstract. We have compiled, collected, and analyzed 31 temperature depth profiles from boreholes in the Atacama desert in central and northern Chile. After screening these profiles, we found that only 9 profiles at 4 different sites were suitable to invert for ground temperature history. For all the sites, no surface temperature variations could be resolved for the period 1500-1800. In the northern coastal region of Chile, there is no perceptible temperature variation at all from 1500 to present. In the northern central Chile region, between 26• S and 28• S, the data suggest a cooling from ∼1850 to ∼1980 followed by a 5 1.9 K warming starting ∼20-40 years BP. This result is consistent with the ground surface temperature histories for Peru and the semiarid regions of South America. The duration of the cooling trend is poorly resolved and it may coincide with a marked short cooling interval in the 1960s that is found in meteorological records. The total warming is greater than that inferred from proxy climate reconstructions for central Chile and southern South America, and by the PMIP3/CMIP5 surface temperature simulations for the north-central Chile grid points. The differences between different climate reconstructions, meteorological 10 records, and models are likely due to differences in spatial and temporal resolution between the various data sets and the models.

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Postglacial Time Calculations from Recent Geothermal Measurements in the Calumet Copper Mines

Cited by 52 publications

References 0 publications

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

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

Climate trends in northern Ontario and Québec from borehole temperature profiles

Recent climate variations in Chile: constraints from borehole temperature profiles

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