HR: 1340h
AN: G33A-0023    [Abstracts]
TI: Interannual-Decadal Changes in the Earth's Dynamic Oblateness: Isolation of the Cryospheric Contribution
AU: * Dickey, J O
EM: jean.dickey@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109
AU: Marcus, S L
EM: steven.marcus@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109
AU: Dyurgerov, M B
EM: Mark.Dyurgerov@Colorado.EDU
AF: Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309
AU: Quinn, K J
EM: kquinn@aer.com
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109
AU: Viron, O d
EM: o.deviron@oma.be
AF: Royal Observatory of Belgium, Av. Circulaire, 3, Brussels, 1180 BR Belgium
AU: Fukumori, I
EM: fukumori@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109
AB: Recent changes in the Earths dynamic oblateness (J2) have shown evidence of pronounced variability on interannual-decadal time scales. In particular, a marked anomaly commencing in 1997 showed an increase in J2 strong enough to temporarily reverse the secular decrease due to post-glacial rebound (Cox and Chao, 2002), indicating an anomalous global mass flux from high to low latitudes. Dickey et al. (2002) showed that glacier melting and oceanic bottom pressure changes made substantial contributions to this anomaly. Data series have since been extended, in particular ocean loading derived from ECCO bottom pressures and the hydrology (Milly, pers. comm.). In our updated results, we show that changes in the oceanic and continental hydrological contributions account for a large portion of the J2 changes on interannual time scales. The changes in the mass balance of small (mountain and sub-polar) glaciers explain the larger and longer-term residual changes in J2. Since J2 has its strongest weighting at the poles, contributions from glacial melting at high latitudes account for most of this signal. We note that the temperate-latitude glaciers, for example in Asia, make a large mass change contribution; however, their contribution to J2 changes is small because of their proximity to the J2 nodal latitude, especially near the Himalayas. The polar ice sheets may also be contributing to oblateness variations; due to the many competing geophysical processes and the large areas involved, however, their net mass balance and gravity changes on interannual-decadal time scales cannot yet be accurately assessed.
DE: 1217 Time variable gravity (7223, 7230)
DE: 1223 Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions (0762, 1218, 3319, 4550)
DE: 1225 Global change from geodesy (1222, 1622, 1630, 1641, 1645, 4556)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
SC: Geodesy [G]
MN: Fall Meeting 2005