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 year1) 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
