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Science 6 December 2002:
Vol. 298. no. 5600, pp. 1975 - 1977
DOI: 10.1126/science.1077777
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Reports

Recent Earth Oblateness Variations: Unraveling Climate and Postglacial Rebound Effects

Jean O. Dickey,1* Steven L. Marcus,1 Olivier de Viron,2 Ichiro Fukumori1

Earth's dynamic oblateness (J2) has been decreasing due to postglacial rebound (PGR). However, J2 began to increase in 1997, indicating a pronounced global-scale mass redistribution within Earth's system. We have determined that the observed increases in J2 are caused primarily by a recent surge in subpolar glacial melting and by mass shifts in the Southern, Pacific, and Indian oceans. When these effects are removed, the residual trend in J2 (-2.9 x 10-11 year-1) becomes consistent with previous estimates of PGR from satellite and eclipse data. The climatic significance of these rapid shifts in glacial and oceanic mass, however, remains to be investigated.

1 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.
2 Royal Observatory of Belgium/FNRS, B-1180 Brussels, Belgium.
*   To whom correspondence should be addressed. E-mail: jean.o.dickey{at}jpl.nasa.gov

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