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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS017 Oral Presentation 2382
The Post-Glacial Warming Signal in Heat Flow
Dr. Will Gosnold
Geology and Geological Engineering University of North Dakota IASPEI
Jacek Majorowicz
We advance the hypothesis that post-glacial warming in northern hemisphere continents may have been
of the order of 10 to15 C rather than 3 to 5 C as is generally accepted in terrestrial heat flow research.
If this hypothesis is correct, some northern hemisphere heat flow values may require revision by as
much as 30 to 60 percent. We present several lines of reasoning that tend to support this hypothesis.
First, analyses of ensembles of heat flow determinations in parts of Europe and North America show a
systematic increase in heat flow with depth. These observations are not from analyses of heat flow
variation in individual boreholes, but are of heat flow determinations at different depths in different
boreholes. In Europe, the increase in heat flow with depth has been observed by analysis of more than
1500 deep boreholes located throughout the Fennoscandian Shield, East European Platform, Danish
Basin, Czech Republic, and . There are significantly fewer deep boreholes in North America, but the
increase in heat flow with depth appears in examination of a suite of 759 sites in the IHFC Global Heat
Flow Database for the region east of the Rocky Mountains and north of latitude 40 N. Second, surface
heat flow values in southern hemisphere shields average approximately 61 mWm-2, but surface heat
flow values in northern hemisphere shields average approximately 37 mWm-2. There must be a physical
or chemical reason for northern and southern shield areas of similar ages to have different heat flow
values. The northern hemisphere post-glacial warming signal may be part of a combination of several
possible explanations. A third line of reasoning is that the signal is subtle and cannot be recognized
using the conventional heat flow practice of determining thermal conductivity and thermal gradients on
only a short section of a borehole. Of special significance to this particular argument is the fact that
two-thirds of all terrestrial heat flow determinations have been made in boreholes less than 1000 m
deep and 87 percent of heat flow determinations in North America have been made in boreholes less
than 500 m deep becomes more critical where. Finally, models T-z profiles based on warming by 15 C
closely reproduce observed T-z profiles in 2 km deep boreholes in a region of North America that lies
along the edge of the Pleistocene ice front.
Keywords: heat flow, post glacial warming