Variations in the Earth's oblateness during the past 28 years

Cheng, Minkang; Tapley, Byron D

doi:10.1029/2004jb003028

Cited by 414 publications

(343 citation statements)

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“…Using the satellite laser ranging (SLR) technique for tracking the orbits of geodetic satellites, a measurement of the time rate of change of the oblateness of the Earth is obtained, which enables the study of large mass redistributions in the system. Using the SLR data from seven satellites, Cheng and Tapley [2004] studied the variation of the J 2 component over a 28-year period. This analysis enabled them to establish the existence of strong ENSO-induced interannual variations over timescales of 4 to 6 years, and led them to the inference of a long-term variation with a period of around 21 years.…”

Section: Earth Rotation and The Late Quaternary Ice-agementioning

confidence: 99%

GRACE era secular trends in Earth rotation parameters: A global scale impact of the global warming process?

Roy

Peltier

2011

Geophys. Res. Lett.

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Recent trends in the two primary anomalies in the rotational state of the planet are analyzed in detail, namely those associated with the speed and direction of polar wander and with the non‐tidal acceleration of the rate of axial rotation (via the measurement of the changing oblateness of the Earth's shape). It is demonstrated that a significant change in the secular trends in both of these independent parameters became evident subsequent to approximately 1992. It is suggested that both parameters might have come to be substantially influenced by mass loss from both the great polar ice sheets, and from the very large number of small ice‐sheets and glaciers that are also being influenced by the global warming phenomenon. The modern values for the secular drifts in those parameters that we estimate are appropriate to the period during which measurements have been made by the satellites of the Gravity Recovery and Climate Experiment (GRACE). These changes in secular rates might greatly assist in understanding why the GRACE‐inferred values of the time derivatives of the degree two and order one Stokes coefficients differ so significantly from those associated with Late Quaternary ice‐age influence.

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Section: Earth Rotation and The Late Quaternary Ice-agementioning

confidence: 99%

GRACE era secular trends in Earth rotation parameters: A global scale impact of the global warming process?

Roy

Peltier

2011

Geophys. Res. Lett.

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“…Since the rate of change due to the action of tidal friction alone may be accurately estimated on the basis of the observed rate of recession of the Moon, using lunar laser ranging, and since the net increase in the length of day as a function of time may be inferred on the basis of the analysis of ancient eclipse observations [e.g., Stephenson and Morrison, 1995], one may infer the action of a nontidal component of the acceleration of rotation, which acts so as to slightly reduce the rate of increase of the length of day due to tidal friction, in the amount (1.6 ± 0.4) Â 10 À22 rad s À1 over the past $2500 years. This nontidal acceleration is equivalent to a value for the time dependence of the degree 2 zonal coefficient in the spherical harmonic expansion of Earth's gravitational field, commonly represented in terms of a parameter denoted _ J 2 , of approximately (À2.67 ± 0.15) Â 10 À11 yr À1 [e.g., Yoder et al, 1983;Cheng et al, 1989;Cheng and Tapley, 2004]. Although a transient departure from this long timescale trend has been noted in apparent association with an especially strong El Niño -Southern Oscillation event [Cox and Chao, 2002], following this event, the system recovered in such a way that the initial trend was reestablished.…”

Section: Introductionmentioning

confidence: 99%

On the origins of Earth rotation anomalies: New insights on the basis of both “paleogeodetic” data and Gravity Recovery and Climate Experiment (GRACE) data

2009

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The theory previously developed to predict the impact on Earth's rotational state of the late Pleistocene glaciation cycle is extended. In particular, we examine the extent to which a departure of the infinite time asymptote of the viscoelastic tidal Love number of degree 2, “k2T,” from the observed “fluid” Love number, “kf,” impacts the theory. A number of tests of the influence of the difference in these Love numbers on theoretical predictions of the model of the glacial isostatic adjustment (GIA) process are explored. Relative sea level history predictions are shown not to be sensitive to the difference even though they are highly sensitive to the influence of the changing rotational state itself. We also explore in detail the accuracy with which the Gravity Recovery and Climate Experiment (GRACE) satellite system is able to observe the global GIA process including the time‐dependent amplitude of the degree 2 and order 1 spherical harmonic components of the gravitational field, the only components that are significantly influenced by rotational effects. It is explicitly shown that the GRACE observation of these properties of the time‐varying gravitational field is sufficiently accurate to rule out the values predicted by the ICE‐5G (VM2) model of Peltier (2004). However, we also note that this model is constrained only by data from an epoch during which modern greenhouse gas induced melting of both the great polar ice‐sheets and small ice sheets and glaciers was not occurring. Such modern loss of grounded continental ice strongly influences the evolving rotational state of the planet and thus the values of the degree 2 and order 1 Stokes coefficients as they are currently being measured by the GRACE satellite system. A series of sensitivity tests are employed to demonstrate this fact. We suggest that the accuracy of scenarios for modern land ice melting may be tested by ensuring that such scenarios conform to the GRACE observations of these crucial time‐dependent Stokes coefficients.

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“…For example, currently VLBI cannot continuously observe and SLR has a few global tracking stations, particularly in the southern hemisphere. Furthermore, laser ranging satellites are not sensitive to the high-frequency variations of low-degree gravity field because of the high altitude of their orbits, e.g., LEGEOS 1/2 with altitude of 6000 km (Cheng and Tapley, 2004). Satellite gravimetry, in particular GRACE, is also restricted in precision and resolution due to its orbital altitude, orbital inclination, hardware noise and filtering methods (Swenson and Wahr, 2006).…”

Section: Challenges and Future Developmentsmentioning

confidence: 99%

“…These data have been widely used in precise orbit determination (POD) of artificial satellites and station motions. In addition, since the low-earth-orbit (LEO) laser ranging satellites are sensitive to the low-degree gravity field, SLR is considered the gold-standard in monitoring geocenter and C 20 (Cheng and Tapley, 2004;Jin et al, 2011b) Earth, which allows us to check certain general relativity principals and explore rotational properties of the moon.…”

Section: Slr/llrmentioning

confidence: 99%

“…Mean sea level rise was observed using TG through the 20th century. Sea-level rise was thought to be driven by a steric component due to the thermal expansion of the oceans and a non-steric component due to fresh water input from the melting of continental ice sheets and glaciers (Holgate and Woodworth, 2004;Church and White, 2006;Feng et al, 2013), that affect our living environments, marine ecosystems, coasts and marshes. However, TG provides the relative sea level variations with respect to the land.…”

Section: Introductionmentioning

confidence: 99%

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Observing and understanding the Earth system variations from space geodesy

Jin

Dam

Wdowinski

2013

Journal of Geodynamics

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a b s t r a c tThe interaction and coupling of the Earth system components that include the atmosphere, hydrosphere, cryosphere, lithosphere, and other fluids in Earth's interior, influence the Earth's shape, gravity field and its rotation (the three pillars of geodesy). The effects of global climate change, such as sea level rise, glacier melting, and geoharzards, also affect these observables. However, observations and models of Earth's system change have large uncertainties due to the lack of direct high temporal-spatial measurements. Nowadays, space geodetic techniques, particularly GNSS, VLBI, SLR, DORIS, InSAR, satellite gravimetry and altimetry provide a unique opportunity to monitor and, therefore, understand the processes and feedback mechanisms of the Earth system with high resolution and precision. In this paper, the status of current space geodetic techniques, some recent observations, and interpretations of those observations in terms of the Earth system are presented. These results include the role of space geodetic techniques, atmospheric-ionospheric sounding, ocean monitoring, hydrologic sensing, cryosphere mapping, crustal deformation and loading displacements, gravity field, geocenter motion, Earth's oblateness variations, Earth rotation and atmospheric-solid earth coupling, etc. The remaining questions and challenges regarding observing and understanding the Earth system are discussed.

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Variations in the Earth's oblateness during the past 28 years

Cited by 414 publications

References 23 publications

GRACE era secular trends in Earth rotation parameters: A global scale impact of the global warming process?

GRACE era secular trends in Earth rotation parameters: A global scale impact of the global warming process?

On the origins of Earth rotation anomalies: New insights on the basis of both “paleogeodetic” data and Gravity Recovery and Climate Experiment (GRACE) data

Observing and understanding the Earth system variations from space geodesy

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