HR: 14:40h
AN: G23A-05    [Abstracts]
TI: Recent Changes in the Dynamic Oblateness (J2) of the Earth: Contributions from the Earth's Subsystems and Their Implications
AU: * Dickey, J O
EM: jean.dickey@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91106 United States
AU: Marcus, S L
EM: steven.marcus@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91106 United States
AU: Quinn, K J
EM: Katy.Quinn@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91106 United States
AU: de Viron, O
EM: deviron@oma.be
AF: Royal Belgium Observatory, 3, avenue Circulaire, Bruxelles, B-1180 Belgium
AU: Fukumori, I
EM: Ichiro.Fukumori@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91106 United States
AU: Dyurgerov, M B
EM: dyurg@tintin.colorado.edu
AF: Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309 United States
AB: Earth's dynamic oblateness (J2) has been decreasing due to post-glacial rebound (PGR). However, an increase began in 1997 (Cox and Chao, Science, 2002) indicating a pronounced change in the global-scale mass redistribution process. Dickey et al. (Science, 2002) have determined that the observed increases in J2 were caused primarily by a surge in sub-polar glacial melting and mass shifts in the Southern Pacific, and Indian Oceans. Recently, the geodetic J2 series has been decreasing rather than increasing, which motivates the further study. Data series have been extended, in particular ocean loading derived from ECCO bottom pressures and hydrology (Milly, pers. comm.). Both glacial and oceanic sources had enhanced upward trends around 1998. The sums of the glacial, oceanic, atmospheric and continental hydrological contributions to J2 are compared with geodetic observations (Cox and Chao, 2002; Cox, pers. comm., 2003). The modeled excitation captures the rise of J2 in the late 1990's as well as its subsequent decrease, even though J2 contributions due to glacial melting maintain a positive slope. Thus it is not necessary for the glaciers to switch to a net positive mass-balance, in order to match the decrease in the observed J2. Special emphasis will be placed on the recent glacier results.
DE: 4500 OCEANOGRAPHY: PHYSICAL
DE: 1800 HYDROLOGY
DE: 1827 Glaciology (1863)
DE: 1223 Ocean/Earth/atmosphere interactions (3339)
DE: 1600 GLOBAL CHANGE (New category)
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting