Constraint on deep mantle viscosity from Lageos acceleration data

Details Constraint on deep mantle viscosity from Lageos acceleration data Constraint on deep mantle viscosity from Lageos acceleration data

Aug 1983

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1983natur.304..434p&link_type=abstract

Nature (ISSN 0028-0836), vol. 304, Aug. 4, 1983, p. 434-436.

Physics

60

Earth Mantle, Lageos (Satellite), Orbital Elements, Satellite Orbits, Viscosity, Acceleration (Physics), Glaciology, Gravitational Fields, Time Dependence

Scientific paper

A residual acceleration in the node of the Lageos satellite orbit attributed to a secular decrease of the degree two component of the earth's gravitational potential field (J2) is demonstrated to be due to Pleistocen deglaciation. The acceleration was found to be within 1.3 milliarcsec/yr sq of -14.7 milliarcsec/yr sq, implying a rate of change per yr of J2 within 0.3 of -3.5 x 10 to the -11th. The detected change is caused by a change in the earth's rotation rate to a degree not fully attributable to lunar tidal interactions. Pleistocene deglaciation produced a 100 m global rise in the sea level, accompanied by a redistribution of matter in the mantle by viscous flow because of the gravity imbalance. An analysis of the average viscosity of the mantle using as a basis isostatic adjustment shows that the viscosity of the lower mantle does not necessarily display a high degree of heterogeneity, although layered convecive circulation with a sharp thermal boundary at 670 km depth cannot be ruled out. A sharp increase in the boundary layer temperature would have to be associated with a large increase in the creep activation energy if the lower mantle viscosity were to be similar to that of the upper mantle.

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