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| Titel |
Mantle Dynamics Studied with Parameterized Prescription From Mineral Physics Database |
| VerfasserIn |
N. Tosi, D. Yuen, R. Wentzcovich, N. deKoker |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250065570
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| Zusammenfassung |
| The incorporation of important thermodynamic and transport properties into mantle
convection models has taken a long time for the community to appreciate, even though it was
first spurred by the high-pressure experimental work at Mainz a quarter of a century ago and
the experimental work at Bayreuth and St. Louis. The two quantities whose effects have yet
to be widely appreciated are thermal expansivity α and thermal conductivity k,
which are shown to impact mantle dynamics and thermal history in more ways than
geoscientists have previously imagined. We have constructed simple parameterization
schemes, which are cast analytically for describing α and k over a wide range of
temperatures and pressures corresponding to the Earth’s mantle. This approach employs the
thermodynamics data set drawn from the VLAB at the University of Minnesota based on
first-principles density functional theory [1] and also recent laboratory data from the
Bayreuth group [2]. Using analytical formulae to determine α and k increases the
computational speed of the convection code with respect to employing pre-calculated
look-up tables and allows us to sweep out a wide parameter space. Our results,
which also incorporate temperature and pressure dependent viscosity show the
following prominent features: 1) The temperature-dependence of α is important in
the upper mantle. It enhances strongly the rising hot plumes and inhibits the cold
downwellings, thus making subduction more difficult for young slabs. 2) The pressure
dependence of α is dominant in the lower mantle. It focuses upwellings and speeds
them up during their upward rise. 3) The temperature-dependence of the thermal
conductivity helps to homogenize the lateral thermal anomalies in cold downwellings and
helps to maintain the heat in the upwellings, thus, in concert with alpha, helps to
encourage fast hot plumes. 4) The lattice thermal conductivity of post-perovskite plays
an important role in heat-transfer in the lower mantle and the Earth’s heat budget
history.
[1] www.vlab.msi.umn.edu
[2] Mantilake M., de Koker N, Frost D.J. and McCammon C.A., 2011. Lattice Thermal
Conductivity of Lower Mantle Minerals and Heat Flux from Earth’s Core. Proceedings of the
National Academy of Sciences, 108, 17901-17904. |
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