Mid‐latitude (30°–60° N) climatic warming inferred by combining borehole temperatures with surface air temperatures

Harris, Robert N.; Chapman, David S.

doi:10.1029/2000gl012348

Cited by 145 publications

(208 citation statements)

References 18 publications

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“…General agreement between GST reconstructions and historical SAT records is well documented [e.g., Huang et al, 2000;Harris and Chapman, 2001;Beltrami, 2002]. Such agreement has given credence to the method of GST reconstruction and to the idea that GST reconstructions reflect the generalized climate history of a region.…”

Section: Introductionmentioning

confidence: 91%

Conduction‐dominated heat transport of the annual temperature signal in soil

et al. 2003

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[1] Conductive heat transport of temperature signals into the subsurface is a central assumption of ground surface temperature (GST) reconstructions derived from presentday temperatures in deep boreholes. Here we test this assumption and its implications for annual relationships between GST and surface air temperature (SAT) by analyzing two decades of shallow soil temperature (0.01-11.7 m) and SAT time series measured at Fargo, North Dakota. We spectrally decompose each of these temperature time series to determine the amplitude and phase of the annual signal at each depth. Conductive heat transport of a harmonic temperature signal in a homogeneous medium is characterized theoretically by exponential amplitude attenuation and linear phase shift with depth. We show that transport of the annual signal in the soil at Fargo follows these theoretical characterizations of conduction closely: the depth dependence of both the natural logarithm of the amplitude and the phase shift are highly linear. Interval wave velocities and thermal diffusivities calculated as functions of depth suggest a diffusivity gradient in the upper meter of the soil. We estimate the annual signal at the ground surface by extrapolating amplitude and phase shift regression lines upward to the surface. We compare this estimate of the annual signal at the ground surface to the annual signal contained in the SAT and show the ground surface signal to be attenuated $20% and negligibly phase shifted relative to the SAT.

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Section: Introductionmentioning

confidence: 91%

Conduction‐dominated heat transport of the annual temperature signal in soil

et al. 2003

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“…In the subsequent section, we investigate how the LGC signal may impact temperature and energy flux histories estimated for the last millennium from BTP analyses that do not account for the LGC impacts. All global analyses of BTPs (Pollack et al, 1996;Harris and Chapman, 2001;Beltrami and Bourlon, 2004) have assumed that the influence of the LGC on BTPs was negligible within the first 600 m of the profiles, the maximum depth that is typically used to estimate last-millennium surface changes. We therefore investigate how studies making these assumptions may or may not include additional biases due to the unaccounted LGC impact.…”

Section: Impact Of Postglacial Warming On the Recent Gsth And Subsurfmentioning

confidence: 99%

“…This characteristic of heat propagation in the terrestrial subsurface has been exploited to estimate past changes in GST and energy fluxes from BTPs measured across all continental regions. Inversion of BTPs to derive GST histories is an operation that transforms a temperaturedepth profile T (t 0 , z) at a given time t 0 (the time of measurement) into a temperature-time profile T (t, z 0 ) at the ground surface z 0 (e.g., Beltrami and Mareschal, 1991;Pollack and Huang, 2000;Huang et al, 2000;Harris and Chapman, 2001;Beltrami, 2002a;Rath and Mottaghy, 2007). If the rock properties are assumed to be vertically homogeneous, depth and time are linked by the thermal diffusivity κ.…”

Section: Theoretical Frameworkmentioning

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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“…The other major observation that remains, if the Arctic reconstruction is not an outlier of northern hemisphere reconstructions, is that surface ground temperatures (SGT) histories inferred from borehole temperatures clearly suggest greater warming since the 18th and 17th centuries than do proxy reconstructions. This discrepancy (see Harris and Chapman [2001] for some possible explanations) needs to be resolved before the potential of combining borehole temperatures with highresolution proxy indicators of climate change can be fully realized.…”

mentioning

confidence: 99%

“…We [Harris and Chapman, 2001] had taken a proxy, Arctic wide summer-weighted annual temperature reconstruction [Overpeck et al, 1997], given in dimensionless sigma units (i.e., normalized deviation from the 1901 -1960 proxy mean in units of standard deviation of the new series for the period 1901 -1960) and represented the reconstruction in our Figure 3 and Table 1 in terms of dimensional temperature units°C.…”

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confidence: 99%