220.127.116.11. Secular Variations
Observations of the secular trend in the orbital excitations contain
a mixture of signals from the solid Earth's return toward isostatic
equilibrium after the removal of large ice loads of the last glacial
maximum and the signals from current ice-sheet mass balance changes
[James and Ivins, 1995] and the related change in global mean sea
Current results from Lageos-1 [Eanes, 1995] indicate that
and from Starlette [Eanes and Bettadpur, 1995]
Cheng et al.  attempted to separate the constraint
equations from these two satellites and 4 others into estimates of
the secular changes in the individual harmonics.
The results are
Analogous results for the odd-degree zonal harmonics have been
obtained; however, these results are more strongly affected by
nongravitational perturbations, and efforts to establish
realistic error estimates are now in progress.