North American climate of the last millennium: Underground temperatures and model comparison



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Stevens, M. Bruce and González Rouco, J. Fidel and Beltrami, Hugo (2008) North American climate of the last millennium: Underground temperatures and model comparison. Journal of geophysical research-earth surface, 113 . ISSN 2169-9003

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General circulation models (GCMs) are currently able to provide physically consistent simulations of millennial climate variability in which estimations of external forcing factors are incorporated as boundary conditions. Climate reconstruction attempts to recover as faithfully as possible past climate variability using a variety of independent and climate-sensitive sources of information. By deriving strategies of comparison between GCM simulations and proxy data, or directly recorded data such as subsurface thermal profiles, the agreement between model and observations can be assessed. Thermal profiles obtained from the boreholes of North America were grouped into eight geographically discrete ensembles and averaged to form robust, representative profiles. The gridded output from the three distinct integrations of the GCM ECHO-g were similarly averaged by region. These simulated, millennial, paleoclimatic histories were then forward modeled to arrive at the subsurface thermal profiles that would result from the temperature trends at the surface. These forward modeled profiles were then compared with the borehole average thermal anomaly profile in each region. In most of the regions studied, the externally forced runs from ECHO-g are in better agreement with underground temperature anomalies than with the control run, suggesting that boreholes are sensitive to external forcing. Not only do ECHO-g simulations demonstrate better agreement with borehole data when considering variable external forcing factors, but ECHO-g also appears to broadly describe qualitative aspects of long-term climatic trends at a regional scale.

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Copyright 2008 by the American Geophysical Union. This research was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC), the Atlantic Innovation Fund (ACOA), and project CGL2005-06097 of the Spanish MEC. M.B.S. was partially funded by a graduate fellowship from the Atlantic Computing Excellence Network (ACEnet). Part of this work was carried out while J.F.G.R. was a James Chair Professor at STFX. J.F.G.R. was additionally funded by a Ramón y Cajal grant. Special thanks to Lisa Kellman, Asfaw Bekele, Dave Risk, and Nick Nickerson for insightful conversations and to Louise Bodri and Robert Harris for their thoughtful reviews of an earlier version of the manuscript.

Uncontrolled Keywords:General-circulation model; Surface air temperatures; Borehole temperatures; Geothermal measurements; Eastern Canada; 5 centuries; Hemisphere temperatures; Past millennium; Global climate; Earth system
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
ID Code:36360
Deposited On:16 Mar 2016 17:32
Last Modified:10 Dec 2018 15:05

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