IERS Global Geophysical Fluids Center (GGFC)

    Special Bureau for Mantle   

Head:  Erik Ivins
 Jet Propulsion Laboratory
Ben Chao, National Central University, Taiwan
Christopher Cox, Raytheon ITSS, and NASA Goddard Space Flight Center
Marianne Greff-Lefftz, Institut de physique du globe de Paris
Richard S. Gross, Jet Propulsion Laboratory
 W. Richard Peltier, Dept. of Physics, University of Toronto

The Special Bureau for Mantle of IERS's GGFC is established to provide services for information and data exchange to facilitate research in the geodynamic effects due to motions in the mantle. Accounting for 68% of the mass and 89% of the moment of inertia of the entire Earth, the solid, but non-rigid, mantle is perpetually in motion. There are motions caused by external forces, including tidal deformation, atmospheric and oceanic loading, and occasional meteorite impacts. For internal processes, volcanic eruptions and pre-seismic, coseismic and post-seismic dislocations associated with an earthquake act on short timescales. On longer timescales, present-day post-glacial rebound, surface processes of soil erosion and deposition, and tectonic activity such as plate motion, orogeny, and internal mantle convection, all transport large masses over long distances. Finally, the entire solid Earth undergoes an equilibrium adjustment in response to the secular slowing down of the Earth's spin due to tidal friction.
 As with any geophysical processes that involve mass transports, these large-scale motions produce variations in Earth's rotation, gravity field, and geocenter. Among them, however, currently only two topics have been extensively investigated:

Co-seismic Excitation of Earth Rotational and Gravitational Changes (B. F. Chao and R. S. Gross)

Glacial Isostatic Adjustment (W. R. Peltier) Effects of Glacial Isostatic Adjustment on the Geopotential (Courtesy E. Ivins)
High Degree Expansion of Glacial Isostatic Adjustment Geoid Change (Courtesy E. Ivins)

SB Atmosphere
SB Core
SB Gravity/Geocenter
SB Hydrology
SB Loading
SB Mantle
SB Oceans
SB Tides