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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 2376
Transient effect of the last glaciation on the continental heat flow
Dr. Shaopeng Huang
Department of Geological Sciences University of Michigan IASPEI
Terrestrial heat flow is a measure of energy flux outward from the interior of Earth. On the one hand, it
carries rich information about the tectonic history, the thermal structure of the lithosphere, and the bulk
chemical composition of the crust on regional and global scales. On the other hand, a heat flow
measurement is subject to the perturbation of various sources including past climate change. The
assessment of the paleoclimate effect on a heat flow measurement requires a good understanding of
the paleoclimate history. Taking advantage of the recent advances in paleoclimate research, I
reevaluate the transient effect of the last glaciation on the continental heat flow. Ice core records (Dahl-
Jensen et al., 1998, Science; Alley, 2000, Quaternary Sci. Rev.) show that the ice sheet temperature in
Greenland was at least 20 degrees Celsius colder at the last glacial maximum than at the present. An
array of GCM models (Winton, 2006, Geophys. Res. Lett.) confirm that climate change is amplified in
arctic areas by almost a factor of two. Accordingly, I approximated the global ground surface
temperature history over the past 50,000 years with an amplitude-reduced version of the Greenland ice
core paleotemperature record, and supplemented the adjusted ice core record with the borehole-proxy
integrated climate reconstruction over the past 500 years (Huang, 2004, Geophys. Res. Lett.) and the
meteorological record over the past 150 years (Brohan et al., 2006, J. Geophys. Res.-Atm.). Additionally
I assumed a progressively increasing uncertainty up to 50% at 50,000 years before present. A set of
subsurface temperature models are then synthesized by forward simulation. The results show that the
apparent heat flow within the upper 2000 m of the crust is systematically lower than the actual
terrestrial heat flow because of the impact of the last glaciation. For example, the estimated
discrepancies between the true and apparent heat flows at the depth of 500 m fall in the range of 14
+/- 6 milliwatts per square meter in these models. The last glaciation transient perturbation is generally
more profound at shallower depths. The uppermost 500 m of the crust embraces over 60% of the
continental measurements residing in the global heat flow database (Pollack et al., 1993, Rev.
Geophys.) of the International Heat Flow Commission. Most of those measurements have not been
corrected for paleoclimate effect. Therefore, the current database might have led to an underestimate
of the continental heat flow by as much as 20%.
Keywords: heat flow, paleoclimate, transient effect