Earth Rotation Variations – Long Period

Gross, R. S.

doi:10.1016/b978-0-444-53802-4.00059-2

Cited by 52 publications

(21 citation statements)

References 575 publications

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“…As described by Wahr et al (2015), conventional pole tide models cannot be applied to the associated drifting component of the centrifugal potential because the use of constant Love numbers is no longer applicable. There are multiple sources for the long-term drift in polar motion, as described by Gross (2007), but the most important is considered to be GIA. As such, models of GIA that include the effects of rotational feedback provide a potential approach for modeling this component of the pole tide.…”

Section: Resultsmentioning

confidence: 99%

“…The T/P model is effectively misrepresenting the effects of long-term drift in polar motion on observed geocentric sea surface height, and we evaluate the impact of this error on observations of regional and GMSL. While there are multiple sources for the observed long-term drift in polar motion (see Gross 2007), glacial isostatic adjustment (GIA) is considered to be the most important. Users interested in the geocentric sea surface displacements associated with rotational feedback from GIA might then correct for these more complex effects using dedicated GIA models (e.g., A et al 2012;Tamisiea 2011), which are not addressed in this paper.…”

Section: Introductionmentioning

confidence: 99%

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Revisiting the pole tide for and from satellite altimetry

Desai

Wahr

Beckley

2015

J Geod

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Satellite altimeter sea surface height observations include the geocentric displacements caused by the pole tide, namely the response of the solid Earth and oceans to polar motion. Most users of these data remove these effects using a model that was developed more than 20 years ago. We describe two improvements to the pole tide model for satellite altimeter measurements. Firstly, we recommend an approach that improves the model for the response of the oceans by including the effects of self-gravitation, loading, and mass conservation. Our recommended approach also specifically includes the previously ignored displacement of the solid Earth due to the load of the ocean response, and includes the effects of geocenter motion. Altogether, this improvement amplifies the modeled geocentric pole tide by 15 %, or up to 2 mm of sea surface height displacement. We validate this improvement using two decades of satellite altimeter measurements. Secondly, we recommend that the altimetry pole tide model exclude geocentric sea surface displacements resulting from the long-term drift in polar motion. The response to this particular component of polar motion requires a more rigorous approach than is used by conventional models. We show that erroneously including the response to this component of polar motion in the pole tide model impacts interpretation of regional sea level rise by ±0.25 mm/year.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Revisiting the pole tide for and from satellite altimetry

Desai

Wahr

Beckley

2015

J Geod

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“…Observations have shown that the rotation axis orientation relative to the terrestrial reference frame, that is, polar motion, varies from semidiurnal to decadal and longer timescales (for a recent review see, e.g., Gross, 2015). The torques that are responsible for the observed polar motion, in particular on timescales of a decade and longer, or the decadal polar motion are the subject of the present study.…”

Section: Introductionmentioning

confidence: 88%

“…Past studies have shown that the atmospheric and oceanic angular momentum variation contribute dominantly to excite rapid polar motion up to interannual timescales (Chao, 1993;Gross, 2015;Ponte et al, 1998;Shindelegger et al, 2013) and that the glacial isostatic adjustment (GIA) causes the polar motion on millennial and longer timescales (e.g., Doubrovine et al, 2012;Mitrovica & Wahr, 2011). Recent results suggest that mass redistributions in the hydrological and cryospheric systems can also excite interannual polar motions (e.g., Chen et al, 2013;Fernández et al, 2007;Meyrath & van Dam 2016;Meyssignac et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Decadal Polar Motion of the Earth Excited by the Convective Outer Core From Geodynamo Simulations

2017

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Long time geodetic observation records show that the orientation of the Earth's rotation axis with respect to the terrestrial reference frame, or polar motion, changes on a broad range of timescales. Apart from external torques from the luni‐solar tides, these changes are excited by interactions among different components of the Earth system. The convective fluid outer core has long been conjectured a likely contributor to the observed polar motion on timescales upward of decades, such as the ∼30 year Markowitz wobble. We investigated the electromagnetic coupling scenario across the core‐mantle boundary via numerical geodynamo simulation for different geodynamo parameters (Rayleigh numbers and magnetic Rossby numbers). Our simulated polar motion varies strongly with the dynamo parameters, while its excitation on decadal timescales appear to converge asymptotically within the adopted range of numerical Rossby numbers. Three strongest asymptotic modes emerge from numerical results, with periods around 30, 40, and 60 years for the prograde excitation and around 24, 30, and 60 years for the retrograde excitation. Their amplitudes are all larger than 5 × 10−8, or approximately 10 milliseconds of arc. The results suggest that the electromagnetic core‐mantle coupling could explain a substantial portion, if not all, of the observed decadal polar motion. In particular, the predicted 60 year polar motion deserves special attention for future observations and studies.

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“…The non-tidal LOD variations, over timescales shorter than about 2 yr, are mainly caused by the dynamic interaction of the solid Earth with its fluid envelopes (atmosphere, oceans and continental hydrology; e.g. Barnes et al, 1983;Höpfner, 1998;Brzeziński et al, 2002;Gross, 2015;Yu et al, 2018). LOD changes are ultimately largest on decadal and longer time scales and involve angular momentum exchanges between the solid mantle and fluid outer core (e.g.…”

Section: Introductionmentioning

confidence: 99%

Semi‐decadal and decadal signals in atmospheric excitation of length‐of‐day

Chen

Ray

et al. 2020

Earth and Space Science

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At timescales shorter than about 2~yr, non‐tidal length‐of‐day (LOD) variations are mainly excited by angular momentum exchanges between the atmospheric, oceanic and continental hydrological fluid envelopes and the underlying solid Earth. On decadal timescales, the dominant excitation sources of LOD variations are from core and mantle coupling. But the excitations of semi‐decadal (specifically 2~8 yr here) signals in length‐of‐day is less clear, and have been characterized by signals with a wide range of periods and varying amplitudes, including a peak at about 5~6 yr. Here sliding window average filtering is applied to isolate semi‐decadal signals from both geodetic technique observed LOD excitation (shorten to geodetic excitation for convenience) and atmospheric LOD excitations. Based on careful comparison between these two excitation series, we find that (1) the 5~6 yr oscillation in geodetic excitations is not periodically consistent; (2) there is a 5~yr oscillation in atmospheric excitation series, and atmosphere can explain all the semi‐decadal oscillation shorter than about 5~yr in geodetic LOD excitations; (3) contributions from atmosphere to 5~6 yr oscillation in LOD variations is small and cannot be clearly determined; (4) it appears that there are some modest long‐period (longer than 10 yr periods) signals in the atmospheric excitations, but these could be artifacts of the models. Then we compare those peaks/troughs epochs in the residual series between geodetic and atmospheric excitations (ROBS_ATM series for short) with the observed geomagnetic jerks, and find that all of the geomagnetic jerks can match one peaks/troughs in the ROBS_ATM series, and they occurred at the same time or within one year before these peaks/troughs. It implies that there is a common origin for the processes giving rise to geomagnetic jerks and the remaining 5~6 yr oscillation in the ROBS_ATM series.

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Earth Rotation Variations – Long Period

Cited by 52 publications

References 575 publications

Revisiting the pole tide for and from satellite altimetry

Revisiting the pole tide for and from satellite altimetry

Decadal Polar Motion of the Earth Excited by the Convective Outer Core From Geodynamo Simulations

Semi‐decadal and decadal signals in atmospheric excitation of length‐of‐day

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