HR: 10:20h
AN: G31C-01 INVITED     [PDF]
TI: Time-Variable Gravity From Satellite-Laser-Ranging and Doppler Measurements: An Update on the Low-Degree Components as Well as the Connections With Geophysical/Climatic Processes
AU: * Cox, C M
EM: ccox@stokes.gsfc.nasa.gov
AF: Raytheon ITSS Company, NASA GSFC Mailstop 926.0, Greenbelt, MD 20771 United States
AU: Chao, B F
EM: chao@bowie.gsfc.nasa.gov
AF: NASA GSFC Space Geodesy Branch, Code 926, Greenbelt, MD 20771 United States
AU: Au, A Y
EM: aau@bowie.gsfc.nasa.gov
AF: Raytheon ITSS Company, NASA GSFC Mailstop 926.0, Greenbelt, MD 20771 United States
AU: Boy, J
EM: boy@bowie.gsfc.nasa.gov
AF: NASA GSFC Space Geodesy Branch, Code 926, Greenbelt, MD 20771 United States
AB: The oblateness of the Earth's gravity field, J2, has long been observed to undergo a slight decrease due to post-glacial rebound of the mantle. Sometime around 1998 this trend reversed quite suddenly. This reversal persisted until 2001, at which point the atmosphere-corrected time series appears to have reversed yet again. Presently, the time series appears to be returning to the value that would nominally have been reached had the anomaly not occurred. This anomaly signifies a large interannual change in global mass distribution whose J2 effect overshadows that of the post-glacial rebound over such timescales. A number of possible causes have been considered, with oceanic mass redistribution as the leading candidate although other effects, such as glacial melting and core effects may be contributing. The amount by which J2 returns to it's nominal value provides a valuable constraint on the separation of the causes, and will be considered. We will present our latest Satellite Laser Ranging and DORIS Doppler derived time series for J2, and various other low-degree harmonic terms, as well as our investigations into the causes. In addition, we will show the comparison of the J2 results with those derived from CHAMP, as computed at NASA GSFC, and the recently released GRACE gravity model.
DE: 1214 Geopotential theory and determination
DE: 1234 Regional and global gravity anomalies and Earth structure
DE: 1635 Oceans (4203)
SC: Geodesy [G]
MN: 2003 Fall Meeting