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Deceleration in the Earth's oblateness
Author(s) -
Cheng Minkang,
Tapley Byron D.,
Ries John C.
Publication year - 2013
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/jgrb.50058
Subject(s) - satellite laser ranging , superposition principle , geodesy , glacier , atmosphere (unit) , satellite , atmospheric sciences , geology , climatology , environmental science , physics , meteorology , laser ranging , laser , astronomy , paleontology , quantum mechanics , optics
For over three decades, satellite laser ranging (SLR) has recorded the global nature of the long‐wavelength mass change within the Earth system. Analysis of the most recent time series of 30 day SLR‐based estimates of Earth's dynamical oblateness, characterized by the gravitational degree‐2 zonal spherical harmonic J 2 , indicates that the long‐term variation of J 2 appears to be more quadratic than linear in nature. The superposition of a quadratic and an 18.6 year variation leads to the “unknown decadal variation” reported by Cheng and Tapley (2004). Although the primary trend is expected to be linear due to global isostatic adjustment, there is an evident deceleration (J ¨ 2 = 18 ± 1 × 10 − 13 / yr 2 ) in the rate of the decrease in J 2 during the last few decades, likely due to changes in the rate of the global mass redistribution from melting of the glaciers and ice sheets as well as mass changes in the atmosphere and ocean.